/*
 * backward.hpp https://github.com/bombela/backward-cpp
 * Copyright 2013 Google Inc. All Rights Reserved.
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this software and associated documentation files (the "Software"), to deal
 * in the Software without restriction, including without limitation the rights
 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
 * copies of the Software, and to permit persons to whom the Software is
 * furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in
 * all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
 * SOFTWARE.
 */

#ifndef H_6B9572DA_A64B_49E6_B234_051480991C89
#define H_6B9572DA_A64B_49E6_B234_051480991C89

#ifndef __cplusplus
#error "It's not going to compile without a C++ compiler..."
#endif

#if defined(BACKWARD_CXX11)
#elif defined(BACKWARD_CXX98)
#else
#if __cplusplus >= 201103L || (defined(_MSC_VER) && _MSC_VER >= 1800)
#define BACKWARD_CXX11
#define BACKWARD_ATLEAST_CXX11
#define BACKWARD_ATLEAST_CXX98
#if __cplusplus >= 201703L || (defined(_MSVC_LANG) && _MSVC_LANG >= 201703L)
#define BACKWARD_ATLEAST_CXX17
#endif
#else
#define BACKWARD_CXX98
#define BACKWARD_ATLEAST_CXX98
#endif
#endif

// You can define one of the following (or leave it to the auto-detection):
//
// #define BACKWARD_SYSTEM_LINUX
//	- specialization for linux
//
// #define BACKWARD_SYSTEM_DARWIN
//	- specialization for Mac OS X 10.5 and later.
//
// #define BACKWARD_SYSTEM_WINDOWS
//  - specialization for Windows (Clang 9 and MSVC2017)
//
// #define BACKWARD_SYSTEM_UNKNOWN
//	- placebo implementation, does nothing.
//
#if defined(BACKWARD_SYSTEM_LINUX)
#elif defined(BACKWARD_SYSTEM_DARWIN)
#elif defined(BACKWARD_SYSTEM_UNKNOWN)
#elif defined(BACKWARD_SYSTEM_WINDOWS)
#else
#if defined(__linux) || defined(__linux__)
#define BACKWARD_SYSTEM_LINUX
#elif defined(__APPLE__)
#define BACKWARD_SYSTEM_DARWIN
#elif defined(_WIN32)
#define BACKWARD_SYSTEM_WINDOWS
#else
#define BACKWARD_SYSTEM_UNKNOWN
#endif
#endif

#define NOINLINE __attribute__((noinline))

#include <algorithm>
#include <cctype>
#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <exception>
#include <fstream>
#include <iomanip>
#include <iostream>
#include <iterator>
#include <limits>
#include <new>
#include <sstream>
#include <streambuf>
#include <string>
#include <vector>

#if defined(BACKWARD_SYSTEM_LINUX)

// On linux, backtrace can back-trace or "walk" the stack using the following
// libraries:
//
// #define BACKWARD_HAS_UNWIND 1
//  - unwind comes from libgcc, but I saw an equivalent inside clang itself.
//  - with unwind, the stacktrace is as accurate as it can possibly be, since
//  this is used by the C++ runtime in gcc/clang for stack unwinding on
//  exception.
//  - normally libgcc is already linked to your program by default.
//
// #define BACKWARD_HAS_LIBUNWIND 1
//  - libunwind provides, in some cases, a more accurate stacktrace as it knows
//  to decode signal handler frames and lets us edit the context registers when
//  unwinding, allowing stack traces over bad function references.
//
// #define BACKWARD_HAS_BACKTRACE == 1
//  - backtrace seems to be a little bit more portable than libunwind, but on
//  linux, it uses unwind anyway, but abstract away a tiny information that is
//  sadly really important in order to get perfectly accurate stack traces.
//  - backtrace is part of the (e)glib library.
//
// The default is:
// #define BACKWARD_HAS_UNWIND == 1
//
// Note that only one of the define should be set to 1 at a time.
//
#if BACKWARD_HAS_UNWIND == 1
#elif BACKWARD_HAS_LIBUNWIND == 1
#elif BACKWARD_HAS_BACKTRACE == 1
#else
#undef BACKWARD_HAS_UNWIND
#define BACKWARD_HAS_UNWIND 1
#undef BACKWARD_HAS_LIBUNWIND
#define BACKWARD_HAS_LIBUNWIND 0
#undef BACKWARD_HAS_BACKTRACE
#define BACKWARD_HAS_BACKTRACE 0
#endif

// On linux, backward can extract detailed information about a stack trace
// using one of the following libraries:
//
// #define BACKWARD_HAS_DW 1
//  - libdw gives you the most juicy details out of your stack traces:
//    - object filename
//    - function name
//    - source filename
//    - line and column numbers
//    - source code snippet (assuming the file is accessible)
//    - variable names (if not optimized out)
//    - variable values (not supported by backward-cpp)
//  - You need to link with the lib "dw":
//    - apt-get install libdw-dev
//    - g++/clang++ -ldw ...
//
// #define BACKWARD_HAS_BFD 1
//  - With libbfd, you get a fair amount of details:
//    - object filename
//    - function name
//    - source filename
//    - line numbers
//    - source code snippet (assuming the file is accessible)
//  - You need to link with the lib "bfd":
//    - apt-get install binutils-dev
//    - g++/clang++ -lbfd ...
//
// #define BACKWARD_HAS_DWARF 1
//  - libdwarf gives you the most juicy details out of your stack traces:
//    - object filename
//    - function name
//    - source filename
//    - line and column numbers
//    - source code snippet (assuming the file is accessible)
//    - variable names (if not optimized out)
//    - variable values (not supported by backward-cpp)
//  - You need to link with the lib "dwarf":
//    - apt-get install libdwarf-dev
//    - g++/clang++ -ldwarf ...
//
// #define BACKWARD_HAS_BACKTRACE_SYMBOL 1
//  - backtrace provides minimal details for a stack trace:
//    - object filename
//    - function name
//  - backtrace is part of the (e)glib library.
//
// The default is:
// #define BACKWARD_HAS_BACKTRACE_SYMBOL == 1
//
// Note that only one of the define should be set to 1 at a time.
//
#if BACKWARD_HAS_DW == 1
#elif BACKWARD_HAS_BFD == 1
#elif BACKWARD_HAS_DWARF == 1
#elif BACKWARD_HAS_BACKTRACE_SYMBOL == 1
#else
#undef BACKWARD_HAS_DW
#define BACKWARD_HAS_DW 0
#undef BACKWARD_HAS_BFD
#define BACKWARD_HAS_BFD 0
#undef BACKWARD_HAS_DWARF
#define BACKWARD_HAS_DWARF 0
#undef BACKWARD_HAS_BACKTRACE_SYMBOL
#define BACKWARD_HAS_BACKTRACE_SYMBOL 1
#endif

#include <cxxabi.h>
#include <fcntl.h>
#ifdef __ANDROID__
//		Old Android API levels define _Unwind_Ptr in both link.h and
// unwind.h 		Rename the one in link.h as we are not going to be using
// it
#define _Unwind_Ptr _Unwind_Ptr_Custom
#include <link.h>
#undef _Unwind_Ptr
#else
#include <link.h>
#endif
#if defined(__ppc__) || defined(__powerpc) || defined(__powerpc__) ||          \
    defined(__POWERPC__)
// Linux kernel header required for the struct pt_regs definition
// to access the NIP (Next Instruction Pointer) register value
#include <asm/ptrace.h>
#endif
#include <signal.h>
#include <sys/stat.h>
#include <syscall.h>
#include <unistd.h>
#ifndef _GNU_SOURCE
#define _GNU_SOURCE
#include <dlfcn.h>
#undef _GNU_SOURCE
#else
#include <dlfcn.h>
#endif

#if BACKWARD_HAS_BFD == 1
//              NOTE: defining PACKAGE{,_VERSION} is required before including
//                    bfd.h on some platforms, see also:
//                    https://sourceware.org/bugzilla/show_bug.cgi?id=14243
#ifndef PACKAGE
#define PACKAGE
#endif
#ifndef PACKAGE_VERSION
#define PACKAGE_VERSION
#endif
#include <bfd.h>
#endif

#if BACKWARD_HAS_DW == 1
#include <dwarf.h>
#include <elfutils/libdw.h>
#include <elfutils/libdwfl.h>
#endif

#if BACKWARD_HAS_DWARF == 1
#include <algorithm>
#include <dwarf.h>
#include <libdwarf.h>
#include <libelf.h>
#include <map>
#endif

#if (BACKWARD_HAS_BACKTRACE == 1) || (BACKWARD_HAS_BACKTRACE_SYMBOL == 1)
// then we shall rely on backtrace
#include <execinfo.h>
#endif

#endif // defined(BACKWARD_SYSTEM_LINUX)

#if defined(BACKWARD_SYSTEM_DARWIN)
// On Darwin, backtrace can back-trace or "walk" the stack using the following
// libraries:
//
// #define BACKWARD_HAS_UNWIND 1
//  - unwind comes from libgcc, but I saw an equivalent inside clang itself.
//  - with unwind, the stacktrace is as accurate as it can possibly be, since
//  this is used by the C++ runtime in gcc/clang for stack unwinding on
//  exception.
//  - normally libgcc is already linked to your program by default.
//
// #define BACKWARD_HAS_LIBUNWIND 1
//  - libunwind comes from clang, which implements an API compatible version.
//  - libunwind provides, in some cases, a more accurate stacktrace as it knows
//  to decode signal handler frames and lets us edit the context registers when
//  unwinding, allowing stack traces over bad function references.
//
// #define BACKWARD_HAS_BACKTRACE == 1
//  - backtrace is available by default, though it does not produce as much
//  information as another library might.
//
// The default is:
// #define BACKWARD_HAS_UNWIND == 1
//
// Note that only one of the define should be set to 1 at a time.
//
#if BACKWARD_HAS_UNWIND == 1
#elif BACKWARD_HAS_BACKTRACE == 1
#elif BACKWARD_HAS_LIBUNWIND == 1
#else
#undef BACKWARD_HAS_UNWIND
#define BACKWARD_HAS_UNWIND 1
#undef BACKWARD_HAS_BACKTRACE
#define BACKWARD_HAS_BACKTRACE 0
#undef BACKWARD_HAS_LIBUNWIND
#define BACKWARD_HAS_LIBUNWIND 0
#endif

// On Darwin, backward can extract detailed information about a stack trace
// using one of the following libraries:
//
// #define BACKWARD_HAS_BACKTRACE_SYMBOL 1
//  - backtrace provides minimal details for a stack trace:
//    - object filename
//    - function name
//
// The default is:
// #define BACKWARD_HAS_BACKTRACE_SYMBOL == 1
//
#if BACKWARD_HAS_BACKTRACE_SYMBOL == 1
#else
#undef BACKWARD_HAS_BACKTRACE_SYMBOL
#define BACKWARD_HAS_BACKTRACE_SYMBOL 1
#endif

#include <cxxabi.h>
#include <fcntl.h>
#include <pthread.h>
#include <signal.h>
#include <sys/stat.h>
#include <unistd.h>

#if (BACKWARD_HAS_BACKTRACE == 1) || (BACKWARD_HAS_BACKTRACE_SYMBOL == 1)
#include <execinfo.h>
#endif
#endif // defined(BACKWARD_SYSTEM_DARWIN)

#if defined(BACKWARD_SYSTEM_WINDOWS)

#include <condition_variable>
#include <mutex>
#include <thread>

#include <basetsd.h>

#ifdef _WIN64
typedef SSIZE_T ssize_t;
#else
typedef int ssize_t;
#endif

#ifndef NOMINMAX
#define NOMINMAX
#endif
#include <windows.h>
#include <winnt.h>

#include <psapi.h>
#include <signal.h>

#ifndef __clang__
#undef NOINLINE
#define NOINLINE __declspec(noinline)
#endif

#ifdef _MSC_VER
#pragma comment(lib, "psapi.lib")
#pragma comment(lib, "dbghelp.lib")
#endif

// Comment / packing is from stackoverflow:
// https://stackoverflow.com/questions/6205981/windows-c-stack-trace-from-a-running-app/28276227#28276227
// Some versions of imagehlp.dll lack the proper packing directives themselves
// so we need to do it.
#pragma pack(push, before_imagehlp, 8)
#include <imagehlp.h>
#pragma pack(pop, before_imagehlp)

// TODO maybe these should be undefined somewhere else?
#undef BACKWARD_HAS_UNWIND
#undef BACKWARD_HAS_BACKTRACE
#if BACKWARD_HAS_PDB_SYMBOL == 1
#else
#undef BACKWARD_HAS_PDB_SYMBOL
#define BACKWARD_HAS_PDB_SYMBOL 1
#endif

#endif

#if BACKWARD_HAS_UNWIND == 1

#include <unwind.h>
// while gcc's unwind.h defines something like that:
//  extern _Unwind_Ptr _Unwind_GetIP (struct _Unwind_Context *);
//  extern _Unwind_Ptr _Unwind_GetIPInfo (struct _Unwind_Context *, int *);
//
// clang's unwind.h defines something like this:
//  uintptr_t _Unwind_GetIP(struct _Unwind_Context* __context);
//
// Even if the _Unwind_GetIPInfo can be linked to, it is not declared, worse we
// cannot just redeclare it because clang's unwind.h doesn't define _Unwind_Ptr
// anyway.
//
// Luckily we can play on the fact that the guard macros have a different name:
#ifdef __CLANG_UNWIND_H
// In fact, this function still comes from libgcc (on my different linux boxes,
// clang links against libgcc).
#include <inttypes.h>
extern "C" uintptr_t _Unwind_GetIPInfo(_Unwind_Context *, int *);
#endif

#endif // BACKWARD_HAS_UNWIND == 1

#if BACKWARD_HAS_LIBUNWIND == 1
#define UNW_LOCAL_ONLY
#include <libunwind.h>
#endif // BACKWARD_HAS_LIBUNWIND == 1

#ifdef BACKWARD_ATLEAST_CXX11
#include <unordered_map>
#include <utility> // for std::swap
namespace backward {
namespace details {
template <typename K, typename V> struct hashtable {
    typedef std::unordered_map<K, V> type;
};
using std::move;
} // namespace details
} // namespace backward
#else // NOT BACKWARD_ATLEAST_CXX11
#define nullptr NULL
#define override
#include <map>
namespace backward {
namespace details {
template <typename K, typename V> struct hashtable {
    typedef std::map<K, V> type;
};
template <typename T> const T &move(const T &v) { return v; }
template <typename T> T &move(T &v) { return v; }
} // namespace details
} // namespace backward
#endif // BACKWARD_ATLEAST_CXX11

namespace backward {
namespace details {
#if defined(BACKWARD_SYSTEM_WINDOWS)
const char kBackwardPathDelimiter[] = ";";
#else
const char kBackwardPathDelimiter[] = ":";
#endif
} // namespace details
} // namespace backward

namespace backward {

namespace system_tag {
struct linux_tag; // seems that I cannot call that "linux" because the name
// is already defined... so I am adding _tag everywhere.
struct darwin_tag;
struct windows_tag;
struct unknown_tag;

#if defined(BACKWARD_SYSTEM_LINUX)
typedef linux_tag current_tag;
#elif defined(BACKWARD_SYSTEM_DARWIN)
typedef darwin_tag current_tag;
#elif defined(BACKWARD_SYSTEM_WINDOWS)
typedef windows_tag current_tag;
#elif defined(BACKWARD_SYSTEM_UNKNOWN)
typedef unknown_tag current_tag;
#else
#error "May I please get my system defines?"
#endif
} // namespace system_tag

namespace trace_resolver_tag {
#if defined(BACKWARD_SYSTEM_LINUX)
struct libdw;
struct libbfd;
struct libdwarf;
struct backtrace_symbol;

#if BACKWARD_HAS_DW == 1
typedef libdw current;
#elif BACKWARD_HAS_BFD == 1
typedef libbfd current;
#elif BACKWARD_HAS_DWARF == 1
typedef libdwarf current;
#elif BACKWARD_HAS_BACKTRACE_SYMBOL == 1
typedef backtrace_symbol current;
#else
#error "You shall not pass, until you know what you want."
#endif
#elif defined(BACKWARD_SYSTEM_DARWIN)
struct backtrace_symbol;

#if BACKWARD_HAS_BACKTRACE_SYMBOL == 1
typedef backtrace_symbol current;
#else
#error "You shall not pass, until you know what you want."
#endif
#elif defined(BACKWARD_SYSTEM_WINDOWS)
struct pdb_symbol;
#if BACKWARD_HAS_PDB_SYMBOL == 1
typedef pdb_symbol current;
#else
#error "You shall not pass, until you know what you want."
#endif
#endif
} // namespace trace_resolver_tag

namespace details {

template <typename T> struct rm_ptr {
    typedef T type;
};

template <typename T> struct rm_ptr<T *> {
    typedef T type;
};

template <typename T> struct rm_ptr<const T *> {
    typedef const T type;
};

template <typename R, typename T, R (*F)(T)> struct deleter {
    template <typename U> void operator()(U &ptr) const { (*F)(ptr); }
};

template <typename T> struct default_delete {
    void operator()(T &ptr) const { delete ptr; }
};

template <typename T, typename Deleter = deleter<void, void *, &::free>>
class handle {
    struct dummy;
    T _val;
    bool _empty;

#ifdef BACKWARD_ATLEAST_CXX11
    handle(const handle &) = delete;
    handle &operator=(const handle &) = delete;
#endif

  public:
    ~handle() {
        if (!_empty) {
            Deleter()(_val);
        }
    }

    explicit handle() : _val(), _empty(true) {}
    explicit handle(T val) : _val(val), _empty(false) {
        if (!_val)
            _empty = true;
    }

#ifdef BACKWARD_ATLEAST_CXX11
    handle(handle &&from) : _empty(true) { swap(from); }
    handle &operator=(handle &&from) {
        swap(from);
        return *this;
    }
#else
    explicit handle(const handle &from) : _empty(true) {
        // some sort of poor man's move semantic.
        swap(const_cast<handle &>(from));
    }
    handle &operator=(const handle &from) {
        // some sort of poor man's move semantic.
        swap(const_cast<handle &>(from));
        return *this;
    }
#endif

    void reset(T new_val) {
        handle tmp(new_val);
        swap(tmp);
    }

    void update(T new_val) {
        _val = new_val;
        _empty = !static_cast<bool>(new_val);
    }

    operator const dummy *() const {
        if (_empty) {
            return nullptr;
        }
        return reinterpret_cast<const dummy *>(_val);
    }
    T get() { return _val; }
    T release() {
        _empty = true;
        return _val;
    }
    void swap(handle &b) {
        using std::swap;
        swap(b._val, _val);     // can throw, we are safe here.
        swap(b._empty, _empty); // should not throw: if you cannot swap two
        // bools without throwing... It's a lost cause anyway!
    }

    T &operator->() { return _val; }
    const T &operator->() const { return _val; }

    typedef typename rm_ptr<T>::type &ref_t;
    typedef const typename rm_ptr<T>::type &const_ref_t;
    ref_t operator*() { return *_val; }
    const_ref_t operator*() const { return *_val; }
    ref_t operator[](size_t idx) { return _val[idx]; }

    // Watch out, we've got a badass over here
    T *operator&() {
        _empty = false;
        return &_val;
    }
};

// Default demangler implementation (do nothing).
template <typename TAG> struct demangler_impl {
    static std::string demangle(const char *funcname) { return funcname; }
};

#if defined(BACKWARD_SYSTEM_LINUX) || defined(BACKWARD_SYSTEM_DARWIN)

template <> struct demangler_impl<system_tag::current_tag> {
    demangler_impl() : _demangle_buffer_length(0) {}

    std::string demangle(const char *funcname) {
        using namespace details;
        char *result = abi::__cxa_demangle(funcname, _demangle_buffer.get(),
                                           &_demangle_buffer_length, nullptr);
        if (result) {
            _demangle_buffer.update(result);
            return result;
        }
        return funcname;
    }

  private:
    details::handle<char *> _demangle_buffer;
    size_t _demangle_buffer_length;
};

#endif // BACKWARD_SYSTEM_LINUX || BACKWARD_SYSTEM_DARWIN

struct demangler : public demangler_impl<system_tag::current_tag> {};

// Split a string on the platform's PATH delimiter.  Example: if delimiter
// is ":" then:
//   ""              --> []
//   ":"             --> ["",""]
//   "::"            --> ["","",""]
//   "/a/b/c"        --> ["/a/b/c"]
//   "/a/b/c:/d/e/f" --> ["/a/b/c","/d/e/f"]
//   etc.
inline std::vector<std::string> split_source_prefixes(const std::string &s) {
    std::vector<std::string> out;
    size_t last = 0;
    size_t next = 0;
    size_t delimiter_size = sizeof(kBackwardPathDelimiter) - 1;
    while ((next = s.find(kBackwardPathDelimiter, last)) != std::string::npos) {
        out.push_back(s.substr(last, next - last));
        last = next + delimiter_size;
    }
    if (last <= s.length()) {
        out.push_back(s.substr(last));
    }
    return out;
}

} // namespace details

/*************** A TRACE ***************/

struct Trace {
    void *addr;
    size_t idx;

    Trace() : addr(nullptr), idx(0) {}

    explicit Trace(void *_addr, size_t _idx) : addr(_addr), idx(_idx) {}
};

struct ResolvedTrace : public Trace {

    struct SourceLoc {
        std::string function;
        std::string filename;
        unsigned line;
        unsigned col;

        SourceLoc() : line(0), col(0) {}

        bool operator==(const SourceLoc &b) const {
            return function == b.function && filename == b.filename &&
                   line == b.line && col == b.col;
        }

        bool operator!=(const SourceLoc &b) const { return !(*this == b); }
    };

    // In which binary object this trace is located.
    std::string object_filename;

    // The function in the object that contain the trace. This is not the same
    // as source.function which can be an function inlined in object_function.
    std::string object_function;

    // The source location of this trace. It is possible for filename to be
    // empty and for line/col to be invalid (value 0) if this information
    // couldn't be deduced, for example if there is no debug information in the
    // binary object.
    SourceLoc source;

    // An optionals list of "inliners". All the successive sources location
    // from where the source location of the trace (the attribute right above)
    // is inlined. It is especially useful when you compiled with optimization.
    typedef std::vector<SourceLoc> source_locs_t;
    source_locs_t inliners;

    ResolvedTrace() : Trace() {}
    ResolvedTrace(const Trace &mini_trace) : Trace(mini_trace) {}
};

/*************** STACK TRACE ***************/

// default implemention.
template <typename TAG> class StackTraceImpl {
  public:
    size_t size() const { return 0; }
    Trace operator[](size_t) const { return Trace(); }
    size_t load_here(size_t = 0) { return 0; }
    size_t load_from(void *, size_t = 0, void * = nullptr, void * = nullptr) {
        return 0;
    }
    size_t thread_id() const { return 0; }
    void skip_n_firsts(size_t) {}
    void *const *begin() const { return nullptr; }
};

class StackTraceImplBase {
  public:
    StackTraceImplBase()
        : _thread_id(0), _skip(0), _context(nullptr), _error_addr(nullptr) {}

    size_t thread_id() const { return _thread_id; }

    void skip_n_firsts(size_t n) { _skip = n; }

  protected:
    void load_thread_info() {
#ifdef BACKWARD_SYSTEM_LINUX
#ifndef __ANDROID__
        _thread_id = static_cast<size_t>(syscall(SYS_gettid));
#else
        _thread_id = static_cast<size_t>(gettid());
#endif
        if (_thread_id == static_cast<size_t>(getpid())) {
            // If the thread is the main one, let's hide that.
            // I like to keep little secret sometimes.
            _thread_id = 0;
        }
#elif defined(BACKWARD_SYSTEM_DARWIN)
        _thread_id = reinterpret_cast<size_t>(pthread_self());
        if (pthread_main_np() == 1) {
            // If the thread is the main one, let's hide that.
            _thread_id = 0;
        }
#endif
    }

    void set_context(void *context) { _context = context; }
    void *context() const { return _context; }

    void set_error_addr(void *error_addr) { _error_addr = error_addr; }
    void *error_addr() const { return _error_addr; }

    size_t skip_n_firsts() const { return _skip; }

  private:
    size_t _thread_id;
    size_t _skip;
    void *_context;
    void *_error_addr;
};

class StackTraceImplHolder : public StackTraceImplBase {
  public:
    size_t size() const {
        return (_stacktrace.size() >= skip_n_firsts())
                   ? _stacktrace.size() - skip_n_firsts()
                   : 0;
    }
    Trace operator[](size_t idx) const {
        if (idx >= size()) {
            return Trace();
        }
        return Trace(_stacktrace[idx + skip_n_firsts()], idx);
    }
    void *const *begin() const {
        if (size()) {
            return &_stacktrace[skip_n_firsts()];
        }
        return nullptr;
    }

  protected:
    std::vector<void *> _stacktrace;
};

#if BACKWARD_HAS_UNWIND == 1

namespace details {

template <typename F> class Unwinder {
  public:
    size_t operator()(F &f, size_t depth) {
        _f = &f;
        _index = -1;
        _depth = depth;
        _Unwind_Backtrace(&this->backtrace_trampoline, this);
        if (_index == -1) {
            // _Unwind_Backtrace has failed to obtain any backtraces
            return 0;
        } else {
            return static_cast<size_t>(_index);
        }
    }

  private:
    F *_f;
    ssize_t _index;
    size_t _depth;

    static _Unwind_Reason_Code backtrace_trampoline(_Unwind_Context *ctx,
                                                    void *self) {
        return (static_cast<Unwinder *>(self))->backtrace(ctx);
    }

    _Unwind_Reason_Code backtrace(_Unwind_Context *ctx) {
        if (_index >= 0 && static_cast<size_t>(_index) >= _depth)
            return _URC_END_OF_STACK;

        int ip_before_instruction = 0;
        uintptr_t ip = _Unwind_GetIPInfo(ctx, &ip_before_instruction);

        if (!ip_before_instruction) {
            // calculating 0-1 for unsigned, looks like a possible bug to
            // sanitizers, so let's do it explicitly:
            if (ip == 0) {
                ip = std::numeric_limits<uintptr_t>::max(); // set it to
                                                            // 0xffff... (as
                                                            // from casting 0-1)
            } else {
                ip -= 1; // else just normally decrement it (no
                         // overflow/underflow will happen)
            }
        }

        if (_index >= 0) { // ignore first frame.
            (*_f)(static_cast<size_t>(_index), reinterpret_cast<void *>(ip));
        }
        _index += 1;
        return _URC_NO_REASON;
    }
};

template <typename F> size_t unwind(F f, size_t depth) {
    Unwinder<F> unwinder;
    return unwinder(f, depth);
}

} // namespace details

template <>
class StackTraceImpl<system_tag::current_tag> : public StackTraceImplHolder {
  public:
    NOINLINE
    size_t load_here(size_t depth = 32, void *context = nullptr,
                     void *error_addr = nullptr) {
        load_thread_info();
        set_context(context);
        set_error_addr(error_addr);
        if (depth == 0) {
            return 0;
        }
        _stacktrace.resize(depth);
        size_t trace_cnt = details::unwind(callback(*this), depth);
        _stacktrace.resize(trace_cnt);
        skip_n_firsts(0);
        return size();
    }
    size_t load_from(void *addr, size_t depth = 32, void *context = nullptr,
                     void *error_addr = nullptr) {
        load_here(depth + 8, context, error_addr);

        for (size_t i = 0; i < _stacktrace.size(); ++i) {
            if (_stacktrace[i] == addr) {
                skip_n_firsts(i);
                break;
            }
        }

        _stacktrace.resize(
            std::min(_stacktrace.size(), skip_n_firsts() + depth));
        return size();
    }

  private:
    struct callback {
        StackTraceImpl &self;
        callback(StackTraceImpl &_self) : self(_self) {}

        void operator()(size_t idx, void *addr) {
            self._stacktrace[idx] = addr;
        }
    };
};

#elif BACKWARD_HAS_LIBUNWIND == 1

template <>
class StackTraceImpl<system_tag::current_tag> : public StackTraceImplHolder {
  public:
    __attribute__((noinline)) size_t load_here(size_t depth = 32,
                                               void *_context = nullptr,
                                               void *_error_addr = nullptr) {
        set_context(_context);
        set_error_addr(_error_addr);
        load_thread_info();
        if (depth == 0) {
            return 0;
        }
        _stacktrace.resize(depth + 1);

        int result = 0;

        unw_context_t ctx;
        size_t index = 0;

        // Add the tail call. If the Instruction Pointer is the crash address it
        // means we got a bad function pointer dereference, so we "unwind" the
        // bad pointer manually by using the return address pointed to by the
        // Stack Pointer as the Instruction Pointer and letting libunwind do
        // the rest

        if (context()) {
            ucontext_t *uctx = reinterpret_cast<ucontext_t *>(context());
#ifdef REG_RIP         // x86_64
            if (uctx->uc_mcontext.gregs[REG_RIP] ==
                reinterpret_cast<greg_t>(error_addr())) {
                uctx->uc_mcontext.gregs[REG_RIP] = *reinterpret_cast<size_t *>(
                    uctx->uc_mcontext.gregs[REG_RSP]);
            }
            _stacktrace[index] =
                reinterpret_cast<void *>(uctx->uc_mcontext.gregs[REG_RIP]);
            ++index;
            ctx = *reinterpret_cast<unw_context_t *>(uctx);
#elif defined(REG_EIP) // x86_32
            if (uctx->uc_mcontext.gregs[REG_EIP] ==
                reinterpret_cast<greg_t>(error_addr())) {
                uctx->uc_mcontext.gregs[REG_EIP] = *reinterpret_cast<size_t *>(
                    uctx->uc_mcontext.gregs[REG_ESP]);
            }
            _stacktrace[index] =
                reinterpret_cast<void *>(uctx->uc_mcontext.gregs[REG_EIP]);
            ++index;
            ctx = *reinterpret_cast<unw_context_t *>(uctx);
#elif defined(__arm__) // clang libunwind/arm
            // libunwind uses its own context type for ARM unwinding.
            // Copy the registers from the signal handler's context so we can
            // unwind
            unw_getcontext(&ctx);
            ctx.regs[UNW_ARM_R0] = uctx->uc_mcontext.arm_r0;
            ctx.regs[UNW_ARM_R1] = uctx->uc_mcontext.arm_r1;
            ctx.regs[UNW_ARM_R2] = uctx->uc_mcontext.arm_r2;
            ctx.regs[UNW_ARM_R3] = uctx->uc_mcontext.arm_r3;
            ctx.regs[UNW_ARM_R4] = uctx->uc_mcontext.arm_r4;
            ctx.regs[UNW_ARM_R5] = uctx->uc_mcontext.arm_r5;
            ctx.regs[UNW_ARM_R6] = uctx->uc_mcontext.arm_r6;
            ctx.regs[UNW_ARM_R7] = uctx->uc_mcontext.arm_r7;
            ctx.regs[UNW_ARM_R8] = uctx->uc_mcontext.arm_r8;
            ctx.regs[UNW_ARM_R9] = uctx->uc_mcontext.arm_r9;
            ctx.regs[UNW_ARM_R10] = uctx->uc_mcontext.arm_r10;
            ctx.regs[UNW_ARM_R11] = uctx->uc_mcontext.arm_fp;
            ctx.regs[UNW_ARM_R12] = uctx->uc_mcontext.arm_ip;
            ctx.regs[UNW_ARM_R13] = uctx->uc_mcontext.arm_sp;
            ctx.regs[UNW_ARM_R14] = uctx->uc_mcontext.arm_lr;
            ctx.regs[UNW_ARM_R15] = uctx->uc_mcontext.arm_pc;

            // If we have crashed in the PC use the LR instead, as this was
            // a bad function dereference
            if (reinterpret_cast<unsigned long>(error_addr()) ==
                uctx->uc_mcontext.arm_pc) {
                ctx.regs[UNW_ARM_R15] =
                    uctx->uc_mcontext.arm_lr - sizeof(unsigned long);
            }
            _stacktrace[index] =
                reinterpret_cast<void *>(ctx.regs[UNW_ARM_R15]);
            ++index;
#elif defined(__APPLE__) && (defined(__arm__) || defined(__arm64__))
            unw_getcontext(&ctx);

            // If the IP is the same as the crash address we have a bad function
            // dereference The caller's address is pointed to by the link
            // pointer, so we dereference that value and set it to be the next
            // frame's IP.
            if (uctx->uc_mcontext->__ss.__pc ==
                reinterpret_cast<__uint64_t>(error_addr())) {
                uctx->uc_mcontext->__ss.__pc = uctx->uc_mcontext->__ss.__lr;
            }

            // 29 general purpose registers
            for (int i = 0; i <= 28; i++) {
                ctx.data[i] = uctx->uc_mcontext->__ss.__x[i];
            }
            ctx.data[29] = uctx->uc_mcontext->__ss.__fp;
            ctx.data[30] = uctx->uc_mcontext->__ss.__lr;
            ctx.data[31] = uctx->uc_mcontext->__ss.__sp;
            ctx.data[32] = uctx->uc_mcontext->__ss.__pc;
            _stacktrace[index] = reinterpret_cast<void *>(ctx.data[32]);
            ++index;
#elif defined(__aarch64__) // gcc libunwind/arm64
            unw_getcontext(&ctx);
            // If the IP is the same as the crash address we have a bad function
            // dereference The caller's address is pointed to by the link
            // pointer, so we dereference that value and set it to be the next
            // frame's IP.
            if (uctx->uc_mcontext.pc ==
                reinterpret_cast<uint64_t>(error_addr())) {
                uctx->uc_mcontext.pc = uctx->uc_mcontext.regs[UNW_TDEP_IP];
            }

            // 29 general purpose registers
            for (int i = UNW_AARCH64_X0; i <= UNW_AARCH64_X28; i++) {
                ctx.uc_mcontext.regs[i] = uctx->uc_mcontext.regs[i];
            }
            ctx.uc_mcontext.sp = uctx->uc_mcontext.sp;
            ctx.uc_mcontext.pc = uctx->uc_mcontext.pc;
            ctx.uc_mcontext.fault_address = uctx->uc_mcontext.fault_address;
            _stacktrace[index] = reinterpret_cast<void *>(ctx.uc_mcontext.pc);
            ++index;
#elif defined(__APPLE__) && defined(__x86_64__)
            unw_getcontext(&ctx);
            // OS X's implementation of libunwind uses its own context object
            // so we need to convert the passed context to libunwind's format
            // (information about the data layout taken from unw_getcontext.s
            // in Apple's libunwind source
            ctx.data[0] = uctx->uc_mcontext->__ss.__rax;
            ctx.data[1] = uctx->uc_mcontext->__ss.__rbx;
            ctx.data[2] = uctx->uc_mcontext->__ss.__rcx;
            ctx.data[3] = uctx->uc_mcontext->__ss.__rdx;
            ctx.data[4] = uctx->uc_mcontext->__ss.__rdi;
            ctx.data[5] = uctx->uc_mcontext->__ss.__rsi;
            ctx.data[6] = uctx->uc_mcontext->__ss.__rbp;
            ctx.data[7] = uctx->uc_mcontext->__ss.__rsp;
            ctx.data[8] = uctx->uc_mcontext->__ss.__r8;
            ctx.data[9] = uctx->uc_mcontext->__ss.__r9;
            ctx.data[10] = uctx->uc_mcontext->__ss.__r10;
            ctx.data[11] = uctx->uc_mcontext->__ss.__r11;
            ctx.data[12] = uctx->uc_mcontext->__ss.__r12;
            ctx.data[13] = uctx->uc_mcontext->__ss.__r13;
            ctx.data[14] = uctx->uc_mcontext->__ss.__r14;
            ctx.data[15] = uctx->uc_mcontext->__ss.__r15;
            ctx.data[16] = uctx->uc_mcontext->__ss.__rip;

            // If the IP is the same as the crash address we have a bad function
            // dereference The caller's address is pointed to by %rsp, so we
            // dereference that value and set it to be the next frame's IP.
            if (uctx->uc_mcontext->__ss.__rip ==
                reinterpret_cast<__uint64_t>(error_addr())) {
                ctx.data[16] = *reinterpret_cast<__uint64_t *>(
                    uctx->uc_mcontext->__ss.__rsp);
            }
            _stacktrace[index] = reinterpret_cast<void *>(ctx.data[16]);
            ++index;
#elif defined(__APPLE__)
            unw_getcontext(&ctx)
                // TODO: Convert the ucontext_t to libunwind's unw_context_t
                // like we do in 64 bits
                if (ctx.uc_mcontext->__ss.__eip ==
                    reinterpret_cast<greg_t>(error_addr())) {
                ctx.uc_mcontext->__ss.__eip = ctx.uc_mcontext->__ss.__esp;
            }
            _stacktrace[index] =
                reinterpret_cast<void *>(ctx.uc_mcontext->__ss.__eip);
            ++index;
#endif
        }

        unw_cursor_t cursor;
        if (context()) {
#if defined(UNW_INIT_SIGNAL_FRAME)
            result = unw_init_local2(&cursor, &ctx, UNW_INIT_SIGNAL_FRAME);
#else
            result = unw_init_local(&cursor, &ctx);
#endif
        } else {
            unw_getcontext(&ctx);
            ;
            result = unw_init_local(&cursor, &ctx);
        }

        if (result != 0)
            return 1;

        unw_word_t ip = 0;

        while (index <= depth && unw_step(&cursor) > 0) {
            result = unw_get_reg(&cursor, UNW_REG_IP, &ip);
            if (result == 0) {
                _stacktrace[index] = reinterpret_cast<void *>(--ip);
                ++index;
            }
        }
        --index;

        _stacktrace.resize(index + 1);
        skip_n_firsts(0);
        return size();
    }

    size_t load_from(void *addr, size_t depth = 32, void *context = nullptr,
                     void *error_addr = nullptr) {
        load_here(depth + 8, context, error_addr);

        for (size_t i = 0; i < _stacktrace.size(); ++i) {
            if (_stacktrace[i] == addr) {
                skip_n_firsts(i);
                _stacktrace[i] = (void *)((uintptr_t)_stacktrace[i]);
                break;
            }
        }

        _stacktrace.resize(
            std::min(_stacktrace.size(), skip_n_firsts() + depth));
        return size();
    }
};

#elif defined(BACKWARD_HAS_BACKTRACE)

template <>
class StackTraceImpl<system_tag::current_tag> : public StackTraceImplHolder {
  public:
    NOINLINE
    size_t load_here(size_t depth = 32, void *context = nullptr,
                     void *error_addr = nullptr) {
        set_context(context);
        set_error_addr(error_addr);
        load_thread_info();
        if (depth == 0) {
            return 0;
        }
        _stacktrace.resize(depth + 1);
        size_t trace_cnt = backtrace(&_stacktrace[0], _stacktrace.size());
        _stacktrace.resize(trace_cnt);
        skip_n_firsts(1);
        return size();
    }

    size_t load_from(void *addr, size_t depth = 32, void *context = nullptr,
                     void *error_addr = nullptr) {
        load_here(depth + 8, context, error_addr);

        for (size_t i = 0; i < _stacktrace.size(); ++i) {
            if (_stacktrace[i] == addr) {
                skip_n_firsts(i);
                _stacktrace[i] = (void *)((uintptr_t)_stacktrace[i] + 1);
                break;
            }
        }

        _stacktrace.resize(
            std::min(_stacktrace.size(), skip_n_firsts() + depth));
        return size();
    }
};

#elif defined(BACKWARD_SYSTEM_WINDOWS)

template <>
class StackTraceImpl<system_tag::current_tag> : public StackTraceImplHolder {
  public:
    // We have to load the machine type from the image info
    // So we first initialize the resolver, and it tells us this info
    void set_machine_type(DWORD machine_type) { machine_type_ = machine_type; }
    void set_context(CONTEXT *ctx) { ctx_ = ctx; }
    void set_thread_handle(HANDLE handle) { thd_ = handle; }

    NOINLINE
    size_t load_here(size_t depth = 32, void *context = nullptr,
                     void *error_addr = nullptr) {
        set_context(static_cast<CONTEXT *>(context));
        set_error_addr(error_addr);
        CONTEXT localCtx; // used when no context is provided

        if (depth == 0) {
            return 0;
        }

        if (!ctx_) {
            ctx_ = &localCtx;
            RtlCaptureContext(ctx_);
        }

        if (!thd_) {
            thd_ = GetCurrentThread();
        }

        HANDLE process = GetCurrentProcess();

        STACKFRAME64 s;
        memset(&s, 0, sizeof(STACKFRAME64));

        // TODO: 32 bit context capture
        s.AddrStack.Mode = AddrModeFlat;
        s.AddrFrame.Mode = AddrModeFlat;
        s.AddrPC.Mode = AddrModeFlat;
#if defined(_M_X64)
        s.AddrPC.Offset = ctx_->Rip;
        s.AddrStack.Offset = ctx_->Rsp;
        s.AddrFrame.Offset = ctx_->Rbp;
#elif defined(_M_ARM64)
        s.AddrPC.Offset = ctx_->Pc;
        s.AddrStack.Offset = ctx_->Sp;
        s.AddrFrame.Offset = ctx_->Fp;
#elif defined(_M_ARM)
        s.AddrPC.Offset = ctx_->Pc;
        s.AddrStack.Offset = ctx_->Sp;
        s.AddrFrame.Offset = ctx_->R11;
#else
        s.AddrPC.Offset = ctx_->Eip;
        s.AddrStack.Offset = ctx_->Esp;
        s.AddrFrame.Offset = ctx_->Ebp;
#endif

        if (!machine_type_) {
#if defined(_M_X64)
            machine_type_ = IMAGE_FILE_MACHINE_AMD64;
#elif defined(_M_ARM64)
            machine_type_ = IMAGE_FILE_MACHINE_ARM64;
#elif defined(_M_ARM)
            machine_type_ = IMAGE_FILE_MACHINE_ARMNT;
#else
            machine_type_ = IMAGE_FILE_MACHINE_I386;
#endif
        }

        for (;;) {
            // NOTE: this only works if PDBs are already loaded!
            SetLastError(0);
            if (!StackWalk64(machine_type_, process, thd_, &s, ctx_, NULL,
                             SymFunctionTableAccess64, SymGetModuleBase64,
                             NULL))
                break;

            if (s.AddrReturn.Offset == 0)
                break;

            _stacktrace.push_back(reinterpret_cast<void *>(s.AddrPC.Offset));

            if (size() >= depth)
                break;
        }

        return size();
    }

    size_t load_from(void *addr, size_t depth = 32, void *context = nullptr,
                     void *error_addr = nullptr) {
        load_here(depth + 8, context, error_addr);

        for (size_t i = 0; i < _stacktrace.size(); ++i) {
            if (_stacktrace[i] == addr) {
                skip_n_firsts(i);
                break;
            }
        }

        _stacktrace.resize(
            std::min(_stacktrace.size(), skip_n_firsts() + depth));
        return size();
    }

  private:
    DWORD machine_type_ = 0;
    HANDLE thd_ = 0;
    CONTEXT *ctx_ = nullptr;
};

#endif

class StackTrace : public StackTraceImpl<system_tag::current_tag> {};

/*************** TRACE RESOLVER ***************/

class TraceResolverImplBase {
  public:
    virtual ~TraceResolverImplBase() {}

    virtual void load_addresses(void *const *addresses, int address_count) {
        (void)addresses;
        (void)address_count;
    }

    template <class ST> void load_stacktrace(ST &st) {
        load_addresses(st.begin(), static_cast<int>(st.size()));
    }

    virtual ResolvedTrace resolve(ResolvedTrace t) { return t; }

  protected:
    std::string demangle(const char *funcname) {
        return _demangler.demangle(funcname);
    }

  private:
    details::demangler _demangler;
};

template <typename TAG> class TraceResolverImpl;

#ifdef BACKWARD_SYSTEM_UNKNOWN

template <>
class TraceResolverImpl<system_tag::unknown_tag>
    : public TraceResolverImplBase {};

#endif

#ifdef BACKWARD_SYSTEM_LINUX

class TraceResolverLinuxBase : public TraceResolverImplBase {
  public:
    TraceResolverLinuxBase()
        : argv0_(get_argv0()), exec_path_(read_symlink("/proc/self/exe")) {}
    std::string resolve_exec_path(Dl_info &symbol_info) const {
        // mutates symbol_info.dli_fname to be filename to open and returns
        // filename to display
        if (symbol_info.dli_fname == argv0_) {
            // dladdr returns argv[0] in dli_fname for symbols contained in
            // the main executable, which is not a valid path if the
            // executable was found by a search of the PATH environment
            // variable; In that case, we actually open /proc/self/exe, which
            // is always the actual executable (even if it was
            // deleted/replaced!) but display the path that /proc/self/exe links
            // to. However, this right away reduces probability of successful
            // symbol resolution, because libbfd may try to find *.debug files
            // in the same dir, in case symbols are stripped. As a result, it
            // may try to find a file /proc/self/<exe_name>.debug, which
            // obviously does not exist. /proc/self/exe is a last resort. First
            // load attempt should go for the original executable file path.
            symbol_info.dli_fname = "/proc/self/exe";
            return exec_path_;
        } else {
            return symbol_info.dli_fname;
        }
    }

  private:
    std::string argv0_;
    std::string exec_path_;

    static std::string get_argv0() {
        std::string argv0;
        std::ifstream ifs("/proc/self/cmdline");
        std::getline(ifs, argv0, '\0');
        return argv0;
    }

    static std::string read_symlink(std::string const &symlink_path) {
        std::string path;
        path.resize(100);

        while (true) {
            ssize_t len =
                ::readlink(symlink_path.c_str(), &*path.begin(), path.size());
            if (len < 0) {
                return "";
            }
            if (static_cast<size_t>(len) == path.size()) {
                path.resize(path.size() * 2);
            } else {
                path.resize(static_cast<std::string::size_type>(len));
                break;
            }
        }

        return path;
    }
};

template <typename STACKTRACE_TAG> class TraceResolverLinuxImpl;

#if BACKWARD_HAS_BACKTRACE_SYMBOL == 1

template <>
class TraceResolverLinuxImpl<trace_resolver_tag::backtrace_symbol>
    : public TraceResolverLinuxBase {
  public:
    void load_addresses(void *const *addresses, int address_count) override {
        if (address_count == 0) {
            return;
        }
        _symbols.reset(backtrace_symbols(addresses, address_count));
    }

    ResolvedTrace resolve(ResolvedTrace trace) override {
        char *filename = _symbols[trace.idx];
        char *funcname = filename;
        while (*funcname && *funcname != '(') {
            funcname += 1;
        }
        trace.object_filename.assign(
            filename,
            funcname); // ok even if funcname is the ending
                       // \0 (then we assign entire string)

        if (*funcname) { // if it's not end of string (e.g. from last frame
                         // ip==0)
            funcname += 1;
            char *funcname_end = funcname;
            while (*funcname_end && *funcname_end != ')' &&
                   *funcname_end != '+') {
                funcname_end += 1;
            }
            *funcname_end = '\0';
            trace.object_function = this->demangle(funcname);
            trace.source.function =
                trace.object_function; // we cannot do better.
        }
        return trace;
    }

  private:
    details::handle<char **> _symbols;
};

#endif // BACKWARD_HAS_BACKTRACE_SYMBOL == 1

#if BACKWARD_HAS_BFD == 1

template <>
class TraceResolverLinuxImpl<trace_resolver_tag::libbfd>
    : public TraceResolverLinuxBase {
  public:
    TraceResolverLinuxImpl() : _bfd_loaded(false) {}

    ResolvedTrace resolve(ResolvedTrace trace) override {
        Dl_info symbol_info;

        // trace.addr is a virtual address in memory pointing to some code.
        // Let's try to find from which loaded object it comes from.
        // The loaded object can be yourself btw.
        if (!dladdr(trace.addr, &symbol_info)) {
            return trace; // dat broken trace...
        }

        // Now we get in symbol_info:
        // .dli_fname:
        //		pathname of the shared object that contains the address.
        // .dli_fbase:
        //		where the object is loaded in memory.
        // .dli_sname:
        //		the name of the nearest symbol to trace.addr, we expect
        // a 		function name.
        // .dli_saddr:
        //		the exact address corresponding to .dli_sname.

        if (symbol_info.dli_sname) {
            trace.object_function = demangle(symbol_info.dli_sname);
        }

        if (!symbol_info.dli_fname) {
            return trace;
        }

        trace.object_filename = resolve_exec_path(symbol_info);
        bfd_fileobject *fobj;
        // Before rushing to resolution need to ensure the executable
        // file still can be used. For that compare inode numbers of
        // what is stored by the executable's file path, and in the
        // dli_fname, which not necessarily equals to the executable.
        // It can be a shared library, or /proc/self/exe, and in the
        // latter case has drawbacks. See the exec path resolution for
        // details. In short - the dli object should be used only as
        // the last resort.
        // If inode numbers are equal, it is known dli_fname and the
        // executable file are the same. This is guaranteed by Linux,
        // because if the executable file is changed/deleted, it will
        // be done in a new inode. The old file will be preserved in
        // /proc/self/exe, and may even have inode 0. The latter can
        // happen if the inode was actually reused, and the file was
        // kept only in the main memory.
        //
        struct stat obj_stat;
        struct stat dli_stat;
        if (stat(trace.object_filename.c_str(), &obj_stat) == 0 &&
            stat(symbol_info.dli_fname, &dli_stat) == 0 &&
            obj_stat.st_ino == dli_stat.st_ino) {
            // The executable file, and the shared object containing the
            // address are the same file. Safe to use the original path.
            // this is preferable. Libbfd will search for stripped debug
            // symbols in the same directory.
            fobj = load_object_with_bfd(trace.object_filename);
        } else {
            // The original object file was *deleted*! The only hope is
            // that the debug symbols are either inside the shared
            // object file, or are in the same directory, and this is
            // not /proc/self/exe.
            fobj = nullptr;
        }
        if (fobj == nullptr || !fobj->handle) {
            fobj = load_object_with_bfd(symbol_info.dli_fname);
            if (!fobj->handle) {
                return trace;
            }
        }

        find_sym_result *details_selected; // to be filled.

        // trace.addr is the next instruction to be executed after returning
        // from the nested stack frame. In C++ this usually relate to the next
        // statement right after the function call that leaded to a new stack
        // frame. This is not usually what you want to see when printing out a
        // stacktrace...
        find_sym_result details_call_site =
            find_symbol_details(fobj, trace.addr, symbol_info.dli_fbase);
        details_selected = &details_call_site;

#if BACKWARD_HAS_UNWIND == 0
        // ...this is why we also try to resolve the symbol that is right
        // before the return address. If we are lucky enough, we will get the
        // line of the function that was called. But if the code is optimized,
        // we might get something absolutely not related since the compiler
        // can reschedule the return address with inline functions and
        // tail-call optimization (among other things that I don't even know
        // or cannot even dream about with my tiny limited brain).
        find_sym_result details_adjusted_call_site = find_symbol_details(
            fobj, (void *)(uintptr_t(trace.addr) - 1), symbol_info.dli_fbase);

        // In debug mode, we should always get the right thing(TM).
        if (details_call_site.found && details_adjusted_call_site.found) {
            // Ok, we assume that details_adjusted_call_site is a better
            // estimation.
            details_selected = &details_adjusted_call_site;
            trace.addr = (void *)(uintptr_t(trace.addr) - 1);
        }

        if (details_selected == &details_call_site && details_call_site.found) {
            // we have to re-resolve the symbol in order to reset some
            // internal state in BFD... so we can call backtrace_inliners
            // thereafter...
            details_call_site =
                find_symbol_details(fobj, trace.addr, symbol_info.dli_fbase);
        }
#endif // BACKWARD_HAS_UNWIND

        if (details_selected->found) {
            if (details_selected->filename) {
                trace.source.filename = details_selected->filename;
            }
            trace.source.line = details_selected->line;

            if (details_selected->funcname) {
                // this time we get the name of the function where the code is
                // located, instead of the function were the address is
                // located. In short, if the code was inlined, we get the
                // function corresponding to the code. Else we already got in
                // trace.function.
                trace.source.function = demangle(details_selected->funcname);

                if (!symbol_info.dli_sname) {
                    // for the case dladdr failed to find the symbol name of
                    // the function, we might as well try to put something
                    // here.
                    trace.object_function = trace.source.function;
                }
            }

            // Maybe the source of the trace got inlined inside the function
            // (trace.source.function). Let's see if we can get all the inlined
            // calls along the way up to the initial call site.
            trace.inliners = backtrace_inliners(fobj, *details_selected);

#if 0
			if (trace.inliners.size() == 0) {
				// Maybe the trace was not inlined... or maybe it was and we
				// are lacking the debug information. Let's try to make the
				// world better and see if we can get the line number of the
				// function (trace.source.function) now.
				//
				// We will get the location of where the function start (to be
				// exact: the first instruction that really start the
				// function), not where the name of the function is defined.
				// This can be quite far away from the name of the function
				// btw.
				//
				// If the source of the function is the same as the source of
				// the trace, we cannot say if the trace was really inlined or
				// not.  However, if the filename of the source is different
				// between the function and the trace... we can declare it as
				// an inliner.  This is not 100% accurate, but better than
				// nothing.

				if (symbol_info.dli_saddr) {
					find_sym_result details = find_symbol_details(fobj,
							symbol_info.dli_saddr,
							symbol_info.dli_fbase);

					if (details.found) {
						ResolvedTrace::SourceLoc diy_inliner;
						diy_inliner.line = details.line;
						if (details.filename) {
							diy_inliner.filename = details.filename;
						}
						if (details.funcname) {
							diy_inliner.function = demangle(details.funcname);
						} else {
							diy_inliner.function = trace.source.function;
						}
						if (diy_inliner != trace.source) {
							trace.inliners.push_back(diy_inliner);
						}
					}
				}
			}
#endif
        }

        return trace;
    }

  private:
    bool _bfd_loaded;

    typedef details::handle<bfd *,
                            details::deleter<bfd_boolean, bfd *, &bfd_close>>
        bfd_handle_t;

    typedef details::handle<asymbol **> bfd_symtab_t;

    struct bfd_fileobject {
        bfd_handle_t handle;
        bfd_vma base_addr;
        bfd_symtab_t symtab;
        bfd_symtab_t dynamic_symtab;
    };

    typedef details::hashtable<std::string, bfd_fileobject>::type
        fobj_bfd_map_t;
    fobj_bfd_map_t _fobj_bfd_map;

    bfd_fileobject *load_object_with_bfd(const std::string &filename_object) {
        using namespace details;

        if (!_bfd_loaded) {
            using namespace details;
            bfd_init();
            _bfd_loaded = true;
        }

        fobj_bfd_map_t::iterator it = _fobj_bfd_map.find(filename_object);
        if (it != _fobj_bfd_map.end()) {
            return &it->second;
        }

        // this new object is empty for now.
        bfd_fileobject *r = &_fobj_bfd_map[filename_object];

        // we do the work temporary in this one;
        bfd_handle_t bfd_handle;

        int fd = open(filename_object.c_str(), O_RDONLY);
        bfd_handle.reset(bfd_fdopenr(filename_object.c_str(), "default", fd));
        if (!bfd_handle) {
            close(fd);
            return r;
        }

        if (!bfd_check_format(bfd_handle.get(), bfd_object)) {
            return r; // not an object? You lose.
        }

        if ((bfd_get_file_flags(bfd_handle.get()) & HAS_SYMS) == 0) {
            return r; // that's what happen when you forget to compile in debug.
        }

        ssize_t symtab_storage_size =
            bfd_get_symtab_upper_bound(bfd_handle.get());

        ssize_t dyn_symtab_storage_size =
            bfd_get_dynamic_symtab_upper_bound(bfd_handle.get());

        if (symtab_storage_size <= 0 && dyn_symtab_storage_size <= 0) {
            return r; // weird, is the file is corrupted?
        }

        bfd_symtab_t symtab, dynamic_symtab;
        ssize_t symcount = 0, dyn_symcount = 0;

        if (symtab_storage_size > 0) {
            symtab.reset(static_cast<bfd_symbol **>(
                malloc(static_cast<size_t>(symtab_storage_size))));
            symcount = bfd_canonicalize_symtab(bfd_handle.get(), symtab.get());
        }

        if (dyn_symtab_storage_size > 0) {
            dynamic_symtab.reset(static_cast<bfd_symbol **>(
                malloc(static_cast<size_t>(dyn_symtab_storage_size))));
            dyn_symcount = bfd_canonicalize_dynamic_symtab(
                bfd_handle.get(), dynamic_symtab.get());
        }

        if (symcount <= 0 && dyn_symcount <= 0) {
            return r; // damned, that's a stripped file that you got there!
        }

        r->handle = move(bfd_handle);
        r->symtab = move(symtab);
        r->dynamic_symtab = move(dynamic_symtab);
        return r;
    }

    struct find_sym_result {
        bool found;
        const char *filename;
        const char *funcname;
        unsigned int line;
    };

    struct find_sym_context {
        TraceResolverLinuxImpl *self;
        bfd_fileobject *fobj;
        void *addr;
        void *base_addr;
        find_sym_result result;
    };

    find_sym_result find_symbol_details(bfd_fileobject *fobj, void *addr,
                                        void *base_addr) {
        find_sym_context context;
        context.self = this;
        context.fobj = fobj;
        context.addr = addr;
        context.base_addr = base_addr;
        context.result.found = false;
        bfd_map_over_sections(fobj->handle.get(), &find_in_section_trampoline,
                              static_cast<void *>(&context));
        return context.result;
    }

    static void find_in_section_trampoline(bfd *, asection *section,
                                           void *data) {
        find_sym_context *context = static_cast<find_sym_context *>(data);
        context->self->find_in_section(
            reinterpret_cast<bfd_vma>(context->addr),
            reinterpret_cast<bfd_vma>(context->base_addr), context->fobj,
            section, context->result);
    }

    void find_in_section(bfd_vma addr, bfd_vma base_addr, bfd_fileobject *fobj,
                         asection *section, find_sym_result &result) {
        if (result.found)
            return;

#ifdef bfd_get_section_flags
        if ((bfd_get_section_flags(fobj->handle.get(), section) & SEC_ALLOC) ==
            0)
#else
        if ((bfd_section_flags(section) & SEC_ALLOC) == 0)
#endif
            return; // a debug section is never loaded automatically.

#ifdef bfd_get_section_vma
        bfd_vma sec_addr = bfd_get_section_vma(fobj->handle.get(), section);
#else
        bfd_vma sec_addr = bfd_section_vma(section);
#endif
#ifdef bfd_get_section_size
        bfd_size_type size = bfd_get_section_size(section);
#else
        bfd_size_type size = bfd_section_size(section);
#endif

        // are we in the boundaries of the section?
        if (addr < sec_addr || addr >= sec_addr + size) {
            addr -= base_addr; // oops, a relocated object, lets try again...
            if (addr < sec_addr || addr >= sec_addr + size) {
                return;
            }
        }

#if defined(__clang__)
#pragma clang diagnostic push
#pragma clang diagnostic ignored "-Wzero-as-null-pointer-constant"
#endif
        if (!result.found && fobj->symtab) {
            result.found = bfd_find_nearest_line(
                fobj->handle.get(), section, fobj->symtab.get(),
                addr - sec_addr, &result.filename, &result.funcname,
                &result.line);
        }

        if (!result.found && fobj->dynamic_symtab) {
            result.found = bfd_find_nearest_line(
                fobj->handle.get(), section, fobj->dynamic_symtab.get(),
                addr - sec_addr, &result.filename, &result.funcname,
                &result.line);
        }
#if defined(__clang__)
#pragma clang diagnostic pop
#endif
    }

    ResolvedTrace::source_locs_t
    backtrace_inliners(bfd_fileobject *fobj, find_sym_result previous_result) {
        // This function can be called ONLY after a SUCCESSFUL call to
        // find_symbol_details. The state is global to the bfd_handle.
        ResolvedTrace::source_locs_t results;
        while (previous_result.found) {
            find_sym_result result;
            result.found =
                bfd_find_inliner_info(fobj->handle.get(), &result.filename,
                                      &result.funcname, &result.line);

            if (result.found) /* and not (
                                    cstrings_eq(previous_result.filename,
                                 result.filename) and
                                 cstrings_eq(previous_result.funcname,
                                 result.funcname) and result.line ==
                                 previous_result.line
                                    )) */
            {
                ResolvedTrace::SourceLoc src_loc;
                src_loc.line = result.line;
                if (result.filename) {
                    src_loc.filename = result.filename;
                }
                if (result.funcname) {
                    src_loc.function = demangle(result.funcname);
                }
                results.push_back(src_loc);
            }
            previous_result = result;
        }
        return results;
    }

    bool cstrings_eq(const char *a, const char *b) {
        if (!a || !b) {
            return false;
        }
        return strcmp(a, b) == 0;
    }
};
#endif // BACKWARD_HAS_BFD == 1

#if BACKWARD_HAS_DW == 1

template <>
class TraceResolverLinuxImpl<trace_resolver_tag::libdw>
    : public TraceResolverLinuxBase {
  public:
    TraceResolverLinuxImpl() : _dwfl_handle_initialized(false) {}

    ResolvedTrace resolve(ResolvedTrace trace) override {
        using namespace details;

        Dwarf_Addr trace_addr = reinterpret_cast<Dwarf_Addr>(trace.addr);

        if (!_dwfl_handle_initialized) {
            // initialize dwfl...
            _dwfl_cb.reset(new Dwfl_Callbacks);
            _dwfl_cb->find_elf = &dwfl_linux_proc_find_elf;
            _dwfl_cb->find_debuginfo = &dwfl_standard_find_debuginfo;
            _dwfl_cb->debuginfo_path = 0;

            _dwfl_handle.reset(dwfl_begin(_dwfl_cb.get()));
            _dwfl_handle_initialized = true;

            if (!_dwfl_handle) {
                return trace;
            }

            // ...from the current process.
            dwfl_report_begin(_dwfl_handle.get());
            int r = dwfl_linux_proc_report(_dwfl_handle.get(), getpid());
            dwfl_report_end(_dwfl_handle.get(), NULL, NULL);
            if (r < 0) {
                return trace;
            }
        }

        if (!_dwfl_handle) {
            return trace;
        }

        // find the module (binary object) that contains the trace's address.
        // This is not using any debug information, but the addresses ranges of
        // all the currently loaded binary object.
        Dwfl_Module *mod = dwfl_addrmodule(_dwfl_handle.get(), trace_addr);
        if (mod) {
            // now that we found it, lets get the name of it, this will be the
            // full path to the running binary or one of the loaded library.
            const char *module_name =
                dwfl_module_info(mod, 0, 0, 0, 0, 0, 0, 0);
            if (module_name) {
                trace.object_filename = module_name;
            }
            // We also look after the name of the symbol, equal or before this
            // address. This is found by walking the symtab. We should get the
            // symbol corresponding to the function (mangled) containing the
            // address. If the code corresponding to the address was inlined,
            // this is the name of the out-most inliner function.
            const char *sym_name = dwfl_module_addrname(mod, trace_addr);
            if (sym_name) {
                trace.object_function = demangle(sym_name);
            }
        }

        // now let's get serious, and find out the source location (file and
        // line number) of the address.

        // This function will look in .debug_aranges for the address and map it
        // to the location of the compilation unit DIE in .debug_info and
        // return it.
        Dwarf_Addr mod_bias = 0;
        Dwarf_Die *cudie = dwfl_module_addrdie(mod, trace_addr, &mod_bias);

#if 1
        if (!cudie) {
            // Sadly clang does not generate the section .debug_aranges, thus
            // dwfl_module_addrdie will fail early. Clang doesn't either set
            // the lowpc/highpc/range info for every compilation unit.
            //
            // So in order to save the world:
            // for every compilation unit, we will iterate over every single
            // DIEs. Normally functions should have a lowpc/highpc/range, which
            // we will use to infer the compilation unit.

            // note that this is probably badly inefficient.
            while ((cudie = dwfl_module_nextcu(mod, cudie, &mod_bias))) {
                Dwarf_Die die_mem;
                Dwarf_Die *fundie =
                    find_fundie_by_pc(cudie, trace_addr - mod_bias, &die_mem);
                if (fundie) {
                    break;
                }
            }
        }
#endif

// #define BACKWARD_I_DO_NOT_RECOMMEND_TO_ENABLE_THIS_HORRIBLE_PIECE_OF_CODE
#ifdef BACKWARD_I_DO_NOT_RECOMMEND_TO_ENABLE_THIS_HORRIBLE_PIECE_OF_CODE
        if (!cudie) {
            // If it's still not enough, lets dive deeper in the shit, and try
            // to save the world again: for every compilation unit, we will
            // load the corresponding .debug_line section, and see if we can
            // find our address in it.

            Dwarf_Addr cfi_bias;
            Dwarf_CFI *cfi_cache = dwfl_module_eh_cfi(mod, &cfi_bias);

            Dwarf_Addr bias;
            while ((cudie = dwfl_module_nextcu(mod, cudie, &bias))) {
                if (dwarf_getsrc_die(cudie, trace_addr - bias)) {

                    // ...but if we get a match, it might be a false positive
                    // because our (address - bias) might as well be valid in a
                    // different compilation unit. So we throw our last card on
                    // the table and lookup for the address into the .eh_frame
                    // section.

                    handle<Dwarf_Frame *> frame;
                    dwarf_cfi_addrframe(cfi_cache, trace_addr - cfi_bias,
                                        &frame);
                    if (frame) {
                        break;
                    }
                }
            }
        }
#endif

        if (!cudie) {
            return trace; // this time we lost the game :/
        }

        // Now that we have a compilation unit DIE, this function will be able
        // to load the corresponding section in .debug_line (if not already
        // loaded) and hopefully find the source location mapped to our
        // address.
        Dwarf_Line *srcloc = dwarf_getsrc_die(cudie, trace_addr - mod_bias);

        if (srcloc) {
            const char *srcfile = dwarf_linesrc(srcloc, 0, 0);
            if (srcfile) {
                trace.source.filename = srcfile;
            }
            int line = 0, col = 0;
            dwarf_lineno(srcloc, &line);
            dwarf_linecol(srcloc, &col);
            trace.source.line = static_cast<unsigned>(line);
            trace.source.col = static_cast<unsigned>(col);
        }

        deep_first_search_by_pc(cudie, trace_addr - mod_bias,
                                inliners_search_cb(trace));
        if (trace.source.function.size() == 0) {
            // fallback.
            trace.source.function = trace.object_function;
        }

        return trace;
    }

  private:
    typedef details::handle<Dwfl *, details::deleter<void, Dwfl *, &dwfl_end>>
        dwfl_handle_t;
    details::handle<Dwfl_Callbacks *, details::default_delete<Dwfl_Callbacks *>>
        _dwfl_cb;
    dwfl_handle_t _dwfl_handle;
    bool _dwfl_handle_initialized;

    // defined here because in C++98, template function cannot take locally
    // defined types... grrr.
    struct inliners_search_cb {
        void operator()(Dwarf_Die *die) {
            switch (dwarf_tag(die)) {
                const char *name;
            case DW_TAG_subprogram:
                if ((name = dwarf_diename(die))) {
                    trace.source.function = name;
                }
                break;

            case DW_TAG_inlined_subroutine:
                ResolvedTrace::SourceLoc sloc;
                Dwarf_Attribute attr_mem;

                if ((name = dwarf_diename(die))) {
                    sloc.function = name;
                }
                if ((name = die_call_file(die))) {
                    sloc.filename = name;
                }

                Dwarf_Word line = 0, col = 0;
                dwarf_formudata(dwarf_attr(die, DW_AT_call_line, &attr_mem),
                                &line);
                dwarf_formudata(dwarf_attr(die, DW_AT_call_column, &attr_mem),
                                &col);
                sloc.line = static_cast<unsigned>(line);
                sloc.col = static_cast<unsigned>(col);

                trace.inliners.push_back(sloc);
                break;
            };
        }
        ResolvedTrace &trace;
        inliners_search_cb(ResolvedTrace &t) : trace(t) {}
    };

    static bool die_has_pc(Dwarf_Die *die, Dwarf_Addr pc) {
        Dwarf_Addr low, high;

        // continuous range
        if (dwarf_hasattr(die, DW_AT_low_pc) &&
            dwarf_hasattr(die, DW_AT_high_pc)) {
            if (dwarf_lowpc(die, &low) != 0) {
                return false;
            }
            if (dwarf_highpc(die, &high) != 0) {
                Dwarf_Attribute attr_mem;
                Dwarf_Attribute *attr =
                    dwarf_attr(die, DW_AT_high_pc, &attr_mem);
                Dwarf_Word value;
                if (dwarf_formudata(attr, &value) != 0) {
                    return false;
                }
                high = low + value;
            }
            return pc >= low && pc < high;
        }

        // non-continuous range.
        Dwarf_Addr base;
        ptrdiff_t offset = 0;
        while ((offset = dwarf_ranges(die, offset, &base, &low, &high)) > 0) {
            if (pc >= low && pc < high) {
                return true;
            }
        }
        return false;
    }

    static Dwarf_Die *find_fundie_by_pc(Dwarf_Die *parent_die, Dwarf_Addr pc,
                                        Dwarf_Die *result) {
        if (dwarf_child(parent_die, result) != 0) {
            return 0;
        }

        Dwarf_Die *die = result;
        do {
            switch (dwarf_tag(die)) {
            case DW_TAG_subprogram:
            case DW_TAG_inlined_subroutine:
                if (die_has_pc(die, pc)) {
                    return result;
                }
            };
            bool declaration = false;
            Dwarf_Attribute attr_mem;
            dwarf_formflag(dwarf_attr(die, DW_AT_declaration, &attr_mem),
                           &declaration);
            if (!declaration) {
                // let's be curious and look deeper in the tree,
                // function are not necessarily at the first level, but
                // might be nested inside a namespace, structure etc.
                Dwarf_Die die_mem;
                Dwarf_Die *indie = find_fundie_by_pc(die, pc, &die_mem);
                if (indie) {
                    *result = die_mem;
                    return result;
                }
            }
        } while (dwarf_siblingof(die, result) == 0);
        return 0;
    }

    template <typename CB>
    static bool deep_first_search_by_pc(Dwarf_Die *parent_die, Dwarf_Addr pc,
                                        CB cb) {
        Dwarf_Die die_mem;
        if (dwarf_child(parent_die, &die_mem) != 0) {
            return false;
        }

        bool branch_has_pc = false;
        Dwarf_Die *die = &die_mem;
        do {
            bool declaration = false;
            Dwarf_Attribute attr_mem;
            dwarf_formflag(dwarf_attr(die, DW_AT_declaration, &attr_mem),
                           &declaration);
            if (!declaration) {
                // let's be curious and look deeper in the tree, function are
                // not necessarily at the first level, but might be nested
                // inside a namespace, structure, a function, an inlined
                // function etc.
                branch_has_pc = deep_first_search_by_pc(die, pc, cb);
            }
            if (!branch_has_pc) {
                branch_has_pc = die_has_pc(die, pc);
            }
            if (branch_has_pc) {
                cb(die);
            }
        } while (dwarf_siblingof(die, &die_mem) == 0);
        return branch_has_pc;
    }

    static const char *die_call_file(Dwarf_Die *die) {
        Dwarf_Attribute attr_mem;
        Dwarf_Word file_idx = 0;

        dwarf_formudata(dwarf_attr(die, DW_AT_call_file, &attr_mem), &file_idx);

        if (file_idx == 0) {
            return 0;
        }

        Dwarf_Die die_mem;
        Dwarf_Die *cudie = dwarf_diecu(die, &die_mem, 0, 0);
        if (!cudie) {
            return 0;
        }

        Dwarf_Files *files = 0;
        size_t nfiles;
        dwarf_getsrcfiles(cudie, &files, &nfiles);
        if (!files) {
            return 0;
        }

        return dwarf_filesrc(files, file_idx, 0, 0);
    }
};
#endif // BACKWARD_HAS_DW == 1

#if BACKWARD_HAS_DWARF == 1

template <>
class TraceResolverLinuxImpl<trace_resolver_tag::libdwarf>
    : public TraceResolverLinuxBase {
  public:
    TraceResolverLinuxImpl() : _dwarf_loaded(false) {}

    ResolvedTrace resolve(ResolvedTrace trace) override {
        // trace.addr is a virtual address in memory pointing to some code.
        // Let's try to find from which loaded object it comes from.
        // The loaded object can be yourself btw.

        Dl_info symbol_info;
        int dladdr_result = 0;
#if defined(__GLIBC__)
        link_map *link_map;
        // We request the link map so we can get information about offsets
        dladdr_result =
            dladdr1(trace.addr, &symbol_info,
                    reinterpret_cast<void **>(&link_map), RTLD_DL_LINKMAP);
#else
        // Android doesn't have dladdr1. Don't use the linker map.
        dladdr_result = dladdr(trace.addr, &symbol_info);
#endif
        if (!dladdr_result) {
            return trace; // dat broken trace...
        }

        // Now we get in symbol_info:
        // .dli_fname:
        //      pathname of the shared object that contains the address.
        // .dli_fbase:
        //      where the object is loaded in memory.
        // .dli_sname:
        //      the name of the nearest symbol to trace.addr, we expect a
        //      function name.
        // .dli_saddr:
        //      the exact address corresponding to .dli_sname.
        //
        // And in link_map:
        // .l_addr:
        //      difference between the address in the ELF file and the address
        //      in memory
        // l_name:
        //      absolute pathname where the object was found

        if (symbol_info.dli_sname) {
            trace.object_function = demangle(symbol_info.dli_sname);
        }

        if (!symbol_info.dli_fname) {
            return trace;
        }

        trace.object_filename = resolve_exec_path(symbol_info);
        dwarf_fileobject &fobj = load_object_with_dwarf(symbol_info.dli_fname);
        if (!fobj.dwarf_handle) {
            return trace; // sad, we couldn't load the object :(
        }

#if defined(__GLIBC__)
        // Convert the address to a module relative one by looking at
        // the module's loading address in the link map
        Dwarf_Addr address = reinterpret_cast<uintptr_t>(trace.addr) -
                             reinterpret_cast<uintptr_t>(link_map->l_addr);
#else
        Dwarf_Addr address = reinterpret_cast<uintptr_t>(trace.addr);
#endif

        if (trace.object_function.empty()) {
            symbol_cache_t::iterator it =
                fobj.symbol_cache.lower_bound(address);

            if (it != fobj.symbol_cache.end()) {
                if (it->first != address) {
                    if (it != fobj.symbol_cache.begin()) {
                        --it;
                    }
                }
                trace.object_function = demangle(it->second.c_str());
            }
        }

        // Get the Compilation Unit DIE for the address
        Dwarf_Die die = find_die(fobj, address);

        if (!die) {
            return trace; // this time we lost the game :/
        }

        // libdwarf doesn't give us direct access to its objects, it always
        // allocates a copy for the caller. We keep that copy alive in a cache
        // and we deallocate it later when it's no longer required.
        die_cache_entry &die_object = get_die_cache(fobj, die);
        if (die_object.isEmpty())
            return trace; // We have no line section for this DIE

        die_linemap_t::iterator it =
            die_object.line_section.lower_bound(address);

        if (it != die_object.line_section.end()) {
            if (it->first != address) {
                if (it == die_object.line_section.begin()) {
                    // If we are on the first item of the line section
                    // but the address does not match it means that
                    // the address is below the range of the DIE. Give up.
                    return trace;
                } else {
                    --it;
                }
            }
        } else {
            return trace; // We didn't find the address.
        }

        // Get the Dwarf_Line that the address points to and call libdwarf
        // to get source file, line and column info.
        Dwarf_Line line = die_object.line_buffer[it->second];
        Dwarf_Error error = DW_DLE_NE;

        char *filename;
        if (dwarf_linesrc(line, &filename, &error) == DW_DLV_OK) {
            trace.source.filename = std::string(filename);
            dwarf_dealloc(fobj.dwarf_handle.get(), filename, DW_DLA_STRING);
        }

        Dwarf_Unsigned number = 0;
        if (dwarf_lineno(line, &number, &error) == DW_DLV_OK) {
            trace.source.line = number;
        } else {
            trace.source.line = 0;
        }

        if (dwarf_lineoff_b(line, &number, &error) == DW_DLV_OK) {
            trace.source.col = number;
        } else {
            trace.source.col = 0;
        }

        std::vector<std::string> namespace_stack;
        deep_first_search_by_pc(fobj, die, address, namespace_stack,
                                inliners_search_cb(trace, fobj, die));

        dwarf_dealloc(fobj.dwarf_handle.get(), die, DW_DLA_DIE);

        return trace;
    }

  public:
    static int close_dwarf(Dwarf_Debug dwarf) {
        return dwarf_finish(dwarf, NULL);
    }

  private:
    bool _dwarf_loaded;

    typedef details::handle<int, details::deleter<int, int, &::close>>
        dwarf_file_t;

    typedef details::handle<Elf *, details::deleter<int, Elf *, &elf_end>>
        dwarf_elf_t;

    typedef details::handle<Dwarf_Debug,
                            details::deleter<int, Dwarf_Debug, &close_dwarf>>
        dwarf_handle_t;

    typedef std::map<Dwarf_Addr, int> die_linemap_t;

    typedef std::map<Dwarf_Off, Dwarf_Off> die_specmap_t;

    struct die_cache_entry {
        die_specmap_t spec_section;
        die_linemap_t line_section;
        Dwarf_Line *line_buffer;
        Dwarf_Signed line_count;
        Dwarf_Line_Context line_context;

        inline bool isEmpty() {
            return line_buffer == NULL || line_count == 0 ||
                   line_context == NULL || line_section.empty();
        }

        die_cache_entry() : line_buffer(0), line_count(0), line_context(0) {}

        ~die_cache_entry() {
            if (line_context) {
                dwarf_srclines_dealloc_b(line_context);
            }
        }
    };

    typedef std::map<Dwarf_Off, die_cache_entry> die_cache_t;

    typedef std::map<uintptr_t, std::string> symbol_cache_t;

    struct dwarf_fileobject {
        dwarf_file_t file_handle;
        dwarf_elf_t elf_handle;
        dwarf_handle_t dwarf_handle;
        symbol_cache_t symbol_cache;

        // Die cache
        die_cache_t die_cache;
        die_cache_entry *current_cu;
    };

    typedef details::hashtable<std::string, dwarf_fileobject>::type
        fobj_dwarf_map_t;
    fobj_dwarf_map_t _fobj_dwarf_map;

    static bool cstrings_eq(const char *a, const char *b) {
        if (!a || !b) {
            return false;
        }
        return strcmp(a, b) == 0;
    }

    dwarf_fileobject &
    load_object_with_dwarf(const std::string &filename_object) {

        if (!_dwarf_loaded) {
            // Set the ELF library operating version
            // If that fails there's nothing we can do
            _dwarf_loaded = elf_version(EV_CURRENT) != EV_NONE;
        }

        fobj_dwarf_map_t::iterator it = _fobj_dwarf_map.find(filename_object);
        if (it != _fobj_dwarf_map.end()) {
            return it->second;
        }

        // this new object is empty for now
        dwarf_fileobject &r = _fobj_dwarf_map[filename_object];

        dwarf_file_t file_handle;
        file_handle.reset(open(filename_object.c_str(), O_RDONLY));
        if (file_handle.get() < 0) {
            return r;
        }

        // Try to get an ELF handle. We need to read the ELF sections
        // because we want to see if there is a .gnu_debuglink section
        // that points to a split debug file
        dwarf_elf_t elf_handle;
        elf_handle.reset(elf_begin(file_handle.get(), ELF_C_READ, NULL));
        if (!elf_handle) {
            return r;
        }

        const char *e_ident = elf_getident(elf_handle.get(), 0);
        if (!e_ident) {
            return r;
        }

        // Get the number of sections
        // We use the new APIs as elf_getshnum is deprecated
        size_t shdrnum = 0;
        if (elf_getshdrnum(elf_handle.get(), &shdrnum) == -1) {
            return r;
        }

        // Get the index to the string section
        size_t shdrstrndx = 0;
        if (elf_getshdrstrndx(elf_handle.get(), &shdrstrndx) == -1) {
            return r;
        }

        std::string debuglink;
        // Iterate through the ELF sections to try to get a gnu_debuglink
        // note and also to cache the symbol table.
        // We go the preprocessor way to avoid having to create templated
        // classes or using gelf (which might throw a compiler error if 64 bit
        // is not supported
#define ELF_GET_DATA(ARCH)                                                     \
    Elf_Scn *elf_section = 0;                                                  \
    Elf_Data *elf_data = 0;                                                    \
    Elf##ARCH##_Shdr *section_header = 0;                                      \
    Elf_Scn *symbol_section = 0;                                               \
    size_t symbol_count = 0;                                                   \
    size_t symbol_strings = 0;                                                 \
    Elf##ARCH##_Sym *symbol = 0;                                               \
    const char *section_name = 0;                                              \
                                                                               \
    while ((elf_section = elf_nextscn(elf_handle.get(), elf_section)) !=       \
           NULL) {                                                             \
        section_header = elf##ARCH##_getshdr(elf_section);                     \
        if (section_header == NULL) {                                          \
            return r;                                                          \
        }                                                                      \
                                                                               \
        if ((section_name = elf_strptr(elf_handle.get(), shdrstrndx,           \
                                       section_header->sh_name)) == NULL) {    \
            return r;                                                          \
        }                                                                      \
                                                                               \
        if (cstrings_eq(section_name, ".gnu_debuglink")) {                     \
            elf_data = elf_getdata(elf_section, NULL);                         \
            if (elf_data && elf_data->d_size > 0) {                            \
                debuglink = std::string(                                       \
                    reinterpret_cast<const char *>(elf_data->d_buf));          \
            }                                                                  \
        }                                                                      \
                                                                               \
        switch (section_header->sh_type) {                                     \
        case SHT_SYMTAB:                                                       \
            symbol_section = elf_section;                                      \
            symbol_count =                                                     \
                section_header->sh_size / section_header->sh_entsize;          \
            symbol_strings = section_header->sh_link;                          \
            break;                                                             \
                                                                               \
        /* We use .dynsyms as a last resort, we prefer .symtab */              \
        case SHT_DYNSYM:                                                       \
            if (!symbol_section) {                                             \
                symbol_section = elf_section;                                  \
                symbol_count =                                                 \
                    section_header->sh_size / section_header->sh_entsize;      \
                symbol_strings = section_header->sh_link;                      \
            }                                                                  \
            break;                                                             \
        }                                                                      \
    }                                                                          \
                                                                               \
    if (symbol_section && symbol_count && symbol_strings) {                    \
        elf_data = elf_getdata(symbol_section, NULL);                          \
        symbol = reinterpret_cast<Elf##ARCH##_Sym *>(elf_data->d_buf);         \
        for (size_t i = 0; i < symbol_count; ++i) {                            \
            int type = ELF##ARCH##_ST_TYPE(symbol->st_info);                   \
            if (type == STT_FUNC && symbol->st_value > 0) {                    \
                r.symbol_cache[symbol->st_value] = std::string(elf_strptr(     \
                    elf_handle.get(), symbol_strings, symbol->st_name));       \
            }                                                                  \
            ++symbol;                                                          \
        }                                                                      \
    }

        if (e_ident[EI_CLASS] == ELFCLASS32) {
            ELF_GET_DATA(32)
        } else if (e_ident[EI_CLASS] == ELFCLASS64) {
            // libelf might have been built without 64 bit support
#if __LIBELF64
            ELF_GET_DATA(64)
#endif
        }

        if (!debuglink.empty()) {
            // We have a debuglink section! Open an elf instance on that
            // file instead. If we can't open the file, then return
            // the elf handle we had already opened.
            dwarf_file_t debuglink_file;
            debuglink_file.reset(open(debuglink.c_str(), O_RDONLY));
            if (debuglink_file.get() > 0) {
                dwarf_elf_t debuglink_elf;
                debuglink_elf.reset(
                    elf_begin(debuglink_file.get(), ELF_C_READ, NULL));

                // If we have a valid elf handle, return the new elf handle
                // and file handle and discard the original ones
                if (debuglink_elf) {
                    elf_handle = move(debuglink_elf);
                    file_handle = move(debuglink_file);
                }
            }
        }

        // Ok, we have a valid ELF handle, let's try to get debug symbols
        Dwarf_Debug dwarf_debug;
        Dwarf_Error error = DW_DLE_NE;
        dwarf_handle_t dwarf_handle;

        int dwarf_result = dwarf_elf_init(elf_handle.get(), DW_DLC_READ, NULL,
                                          NULL, &dwarf_debug, &error);

        // We don't do any special handling for DW_DLV_NO_ENTRY specially.
        // If we get an error, or the file doesn't have debug information
        // we just return.
        if (dwarf_result != DW_DLV_OK) {
            return r;
        }

        dwarf_handle.reset(dwarf_debug);

        r.file_handle = move(file_handle);
        r.elf_handle = move(elf_handle);
        r.dwarf_handle = move(dwarf_handle);

        return r;
    }

    die_cache_entry &get_die_cache(dwarf_fileobject &fobj, Dwarf_Die die) {
        Dwarf_Error error = DW_DLE_NE;

        // Get the die offset, we use it as the cache key
        Dwarf_Off die_offset;
        if (dwarf_dieoffset(die, &die_offset, &error) != DW_DLV_OK) {
            die_offset = 0;
        }

        die_cache_t::iterator it = fobj.die_cache.find(die_offset);

        if (it != fobj.die_cache.end()) {
            fobj.current_cu = &it->second;
            return it->second;
        }

        die_cache_entry &de = fobj.die_cache[die_offset];
        fobj.current_cu = &de;

        Dwarf_Addr line_addr;
        Dwarf_Small table_count;

        // The addresses in the line section are not fully sorted (they might
        // be sorted by block of code belonging to the same file), which makes
        // it necessary to do so before searching is possible.
        //
        // As libdwarf allocates a copy of everything, let's get the contents
        // of the line section and keep it around. We also create a map of
        // program counter to line table indices so we can search by address
        // and get the line buffer index.
        //
        // To make things more difficult, the same address can span more than
        // one line, so we need to keep the index pointing to the first line
        // by using insert instead of the map's [ operator.

        // Get the line context for the DIE
        if (dwarf_srclines_b(die, 0, &table_count, &de.line_context, &error) ==
            DW_DLV_OK) {
            // Get the source lines for this line context, to be deallocated
            // later
            if (dwarf_srclines_from_linecontext(de.line_context,
                                                &de.line_buffer, &de.line_count,
                                                &error) == DW_DLV_OK) {

                // Add all the addresses to our map
                for (int i = 0; i < de.line_count; i++) {
                    if (dwarf_lineaddr(de.line_buffer[i], &line_addr, &error) !=
                        DW_DLV_OK) {
                        line_addr = 0;
                    }
                    de.line_section.insert(
                        std::pair<Dwarf_Addr, int>(line_addr, i));
                }
            }
        }

        // For each CU, cache the function DIEs that contain the
        // DW_AT_specification attribute. When building with -g3 the function
        // DIEs are separated in declaration and specification, with the
        // declaration containing only the name and parameters and the
        // specification the low/high pc and other compiler attributes.
        //
        // We cache those specifications so we don't skip over the declarations,
        // because they have no pc, and we can do namespace resolution for
        // DWARF function names.
        Dwarf_Debug dwarf = fobj.dwarf_handle.get();
        Dwarf_Die current_die = 0;
        if (dwarf_child(die, &current_die, &error) == DW_DLV_OK) {
            for (;;) {
                Dwarf_Die sibling_die = 0;

                Dwarf_Half tag_value;
                dwarf_tag(current_die, &tag_value, &error);

                if (tag_value == DW_TAG_subprogram ||
                    tag_value == DW_TAG_inlined_subroutine) {

                    Dwarf_Bool has_attr = 0;
                    if (dwarf_hasattr(current_die, DW_AT_specification,
                                      &has_attr, &error) == DW_DLV_OK) {
                        if (has_attr) {
                            Dwarf_Attribute attr_mem;
                            if (dwarf_attr(current_die, DW_AT_specification,
                                           &attr_mem, &error) == DW_DLV_OK) {
                                Dwarf_Off spec_offset = 0;
                                if (dwarf_formref(attr_mem, &spec_offset,
                                                  &error) == DW_DLV_OK) {
                                    Dwarf_Off spec_die_offset;
                                    if (dwarf_dieoffset(current_die,
                                                        &spec_die_offset,
                                                        &error) == DW_DLV_OK) {
                                        de.spec_section[spec_offset] =
                                            spec_die_offset;
                                    }
                                }
                            }
                            dwarf_dealloc(dwarf, attr_mem, DW_DLA_ATTR);
                        }
                    }
                }

                int result =
                    dwarf_siblingof(dwarf, current_die, &sibling_die, &error);
                if (result == DW_DLV_ERROR) {
                    break;
                } else if (result == DW_DLV_NO_ENTRY) {
                    break;
                }

                if (current_die != die) {
                    dwarf_dealloc(dwarf, current_die, DW_DLA_DIE);
                    current_die = 0;
                }

                current_die = sibling_die;
            }
        }
        return de;
    }

    static Dwarf_Die get_referenced_die(Dwarf_Debug dwarf, Dwarf_Die die,
                                        Dwarf_Half attr, bool global) {
        Dwarf_Error error = DW_DLE_NE;
        Dwarf_Attribute attr_mem;

        Dwarf_Die found_die = NULL;
        if (dwarf_attr(die, attr, &attr_mem, &error) == DW_DLV_OK) {
            Dwarf_Off offset;
            int result = 0;
            if (global) {
                result = dwarf_global_formref(attr_mem, &offset, &error);
            } else {
                result = dwarf_formref(attr_mem, &offset, &error);
            }

            if (result == DW_DLV_OK) {
                if (dwarf_offdie(dwarf, offset, &found_die, &error) !=
                    DW_DLV_OK) {
                    found_die = NULL;
                }
            }
            dwarf_dealloc(dwarf, attr_mem, DW_DLA_ATTR);
        }
        return found_die;
    }

    static std::string get_referenced_die_name(Dwarf_Debug dwarf, Dwarf_Die die,
                                               Dwarf_Half attr, bool global) {
        Dwarf_Error error = DW_DLE_NE;
        std::string value;

        Dwarf_Die found_die = get_referenced_die(dwarf, die, attr, global);

        if (found_die) {
            char *name;
            if (dwarf_diename(found_die, &name, &error) == DW_DLV_OK) {
                if (name) {
                    value = std::string(name);
                }
                dwarf_dealloc(dwarf, name, DW_DLA_STRING);
            }
            dwarf_dealloc(dwarf, found_die, DW_DLA_DIE);
        }

        return value;
    }

    // Returns a spec DIE linked to the passed one. The caller should
    // deallocate the DIE
    static Dwarf_Die get_spec_die(dwarf_fileobject &fobj, Dwarf_Die die) {
        Dwarf_Debug dwarf = fobj.dwarf_handle.get();
        Dwarf_Error error = DW_DLE_NE;
        Dwarf_Off die_offset;
        if (fobj.current_cu &&
            dwarf_die_CU_offset(die, &die_offset, &error) == DW_DLV_OK) {
            die_specmap_t::iterator it =
                fobj.current_cu->spec_section.find(die_offset);

            // If we have a DIE that completes the current one, check if
            // that one has the pc we are looking for
            if (it != fobj.current_cu->spec_section.end()) {
                Dwarf_Die spec_die = 0;
                if (dwarf_offdie(dwarf, it->second, &spec_die, &error) ==
                    DW_DLV_OK) {
                    return spec_die;
                }
            }
        }

        // Maybe we have an abstract origin DIE with the function information?
        return get_referenced_die(fobj.dwarf_handle.get(), die,
                                  DW_AT_abstract_origin, true);
    }

    static bool die_has_pc(dwarf_fileobject &fobj, Dwarf_Die die,
                           Dwarf_Addr pc) {
        Dwarf_Addr low_pc = 0, high_pc = 0;
        Dwarf_Half high_pc_form = 0;
        Dwarf_Form_Class return_class;
        Dwarf_Error error = DW_DLE_NE;
        Dwarf_Debug dwarf = fobj.dwarf_handle.get();
        bool has_lowpc = false;
        bool has_highpc = false;
        bool has_ranges = false;

        if (dwarf_lowpc(die, &low_pc, &error) == DW_DLV_OK) {
            // If we have a low_pc check if there is a high pc.
            // If we don't have a high pc this might mean we have a base
            // address for the ranges list or just an address.
            has_lowpc = true;

            if (dwarf_highpc_b(die, &high_pc, &high_pc_form, &return_class,
                               &error) == DW_DLV_OK) {
                // We do have a high pc. In DWARF 4+ this is an offset from the
                // low pc, but in earlier versions it's an absolute address.

                has_highpc = true;
                // In DWARF 2/3 this would be a DW_FORM_CLASS_ADDRESS
                if (return_class == DW_FORM_CLASS_CONSTANT) {
                    high_pc = low_pc + high_pc;
                }

                // We have low and high pc, check if our address
                // is in that range
                return pc >= low_pc && pc < high_pc;
            }
        } else {
            // Reset the low_pc, in case dwarf_lowpc failing set it to some
            // undefined value.
            low_pc = 0;
        }

        // Check if DW_AT_ranges is present and search for the PC in the
        // returned ranges list. We always add the low_pc, as it not set it will
        // be 0, in case we had a DW_AT_low_pc and DW_AT_ranges pair
        bool result = false;

        Dwarf_Attribute attr;
        if (dwarf_attr(die, DW_AT_ranges, &attr, &error) == DW_DLV_OK) {

            Dwarf_Off offset;
            if (dwarf_global_formref(attr, &offset, &error) == DW_DLV_OK) {
                Dwarf_Ranges *ranges;
                Dwarf_Signed ranges_count = 0;
                Dwarf_Unsigned byte_count = 0;

                if (dwarf_get_ranges_a(dwarf, offset, die, &ranges,
                                       &ranges_count, &byte_count,
                                       &error) == DW_DLV_OK) {
                    has_ranges = ranges_count != 0;
                    for (int i = 0; i < ranges_count; i++) {
                        if (ranges[i].dwr_addr1 != 0 &&
                            pc >= ranges[i].dwr_addr1 + low_pc &&
                            pc < ranges[i].dwr_addr2 + low_pc) {
                            result = true;
                            break;
                        }
                    }
                    dwarf_ranges_dealloc(dwarf, ranges, ranges_count);
                }
            }
        }

        // Last attempt. We might have a single address set as low_pc.
        if (!result && low_pc != 0 && pc == low_pc) {
            result = true;
        }

        // If we don't have lowpc, highpc and ranges maybe this DIE is a
        // declaration that relies on a DW_AT_specification DIE that happens
        // later. Use the specification cache we filled when we loaded this CU.
        if (!result && (!has_lowpc && !has_highpc && !has_ranges)) {
            Dwarf_Die spec_die = get_spec_die(fobj, die);
            if (spec_die) {
                result = die_has_pc(fobj, spec_die, pc);
                dwarf_dealloc(dwarf, spec_die, DW_DLA_DIE);
            }
        }

        return result;
    }

    static void get_type(Dwarf_Debug dwarf, Dwarf_Die die, std::string &type) {
        Dwarf_Error error = DW_DLE_NE;

        Dwarf_Die child = 0;
        if (dwarf_child(die, &child, &error) == DW_DLV_OK) {
            get_type(dwarf, child, type);
        }

        if (child) {
            type.insert(0, "::");
            dwarf_dealloc(dwarf, child, DW_DLA_DIE);
        }

        char *name;
        if (dwarf_diename(die, &name, &error) == DW_DLV_OK) {
            type.insert(0, std::string(name));
            dwarf_dealloc(dwarf, name, DW_DLA_STRING);
        } else {
            type.insert(0, "<unknown>");
        }
    }

    static std::string get_type_by_signature(Dwarf_Debug dwarf, Dwarf_Die die) {
        Dwarf_Error error = DW_DLE_NE;

        Dwarf_Sig8 signature;
        Dwarf_Bool has_attr = 0;
        if (dwarf_hasattr(die, DW_AT_signature, &has_attr, &error) ==
            DW_DLV_OK) {
            if (has_attr) {
                Dwarf_Attribute attr_mem;
                if (dwarf_attr(die, DW_AT_signature, &attr_mem, &error) ==
                    DW_DLV_OK) {
                    if (dwarf_formsig8(attr_mem, &signature, &error) !=
                        DW_DLV_OK) {
                        return std::string("<no type signature>");
                    }
                }
                dwarf_dealloc(dwarf, attr_mem, DW_DLA_ATTR);
            }
        }

        Dwarf_Unsigned next_cu_header;
        Dwarf_Sig8 tu_signature;
        std::string result;
        bool found = false;

        while (dwarf_next_cu_header_d(dwarf, 0, 0, 0, 0, 0, 0, 0, &tu_signature,
                                      0, &next_cu_header, 0,
                                      &error) == DW_DLV_OK) {

            if (strncmp(signature.signature, tu_signature.signature, 8) == 0) {
                Dwarf_Die type_cu_die = 0;
                if (dwarf_siblingof_b(dwarf, 0, 0, &type_cu_die, &error) ==
                    DW_DLV_OK) {
                    Dwarf_Die child_die = 0;
                    if (dwarf_child(type_cu_die, &child_die, &error) ==
                        DW_DLV_OK) {
                        get_type(dwarf, child_die, result);
                        found = !result.empty();
                        dwarf_dealloc(dwarf, child_die, DW_DLA_DIE);
                    }
                    dwarf_dealloc(dwarf, type_cu_die, DW_DLA_DIE);
                }
            }
        }

        if (found) {
            while (dwarf_next_cu_header_d(dwarf, 0, 0, 0, 0, 0, 0, 0, 0, 0,
                                          &next_cu_header, 0,
                                          &error) == DW_DLV_OK) {
                // Reset the cu header state. Unfortunately, libdwarf's
                // next_cu_header API keeps its own iterator per Dwarf_Debug
                // that can't be reset. We need to keep fetching elements until
                // the end.
            }
        } else {
            // If we couldn't resolve the type just print out the signature
            std::ostringstream string_stream;
            string_stream << "<0x" << std::hex << std::setfill('0');
            for (int i = 0; i < 8; ++i) {
                string_stream << std::setw(2) << std::hex
                              << (int)(unsigned char)(signature.signature[i]);
            }
            string_stream << ">";
            result = string_stream.str();
        }
        return result;
    }

    struct type_context_t {
        bool is_const;
        bool is_typedef;
        bool has_type;
        bool has_name;
        std::string text;

        type_context_t()
            : is_const(false), is_typedef(false), has_type(false),
              has_name(false) {}
    };

    // Types are resolved from right to left: we get the variable name first
    // and then all specifiers (like const or pointer) in a chain of DW_AT_type
    // DIEs. Call this function recursively until we get a complete type
    // string.
    static void set_parameter_string(dwarf_fileobject &fobj, Dwarf_Die die,
                                     type_context_t &context) {
        char *name;
        Dwarf_Error error = DW_DLE_NE;

        // typedefs contain also the base type, so we skip it and only
        // print the typedef name
        if (!context.is_typedef) {
            if (dwarf_diename(die, &name, &error) == DW_DLV_OK) {
                if (!context.text.empty()) {
                    context.text.insert(0, " ");
                }
                context.text.insert(0, std::string(name));
                dwarf_dealloc(fobj.dwarf_handle.get(), name, DW_DLA_STRING);
            }
        } else {
            context.is_typedef = false;
            context.has_type = true;
            if (context.is_const) {
                context.text.insert(0, "const ");
                context.is_const = false;
            }
        }

        bool next_type_is_const = false;
        bool is_keyword = true;

        Dwarf_Half tag = 0;
        Dwarf_Bool has_attr = 0;
        if (dwarf_tag(die, &tag, &error) == DW_DLV_OK) {
            switch (tag) {
            case DW_TAG_structure_type:
            case DW_TAG_union_type:
            case DW_TAG_class_type:
            case DW_TAG_enumeration_type:
                context.has_type = true;
                if (dwarf_hasattr(die, DW_AT_signature, &has_attr, &error) ==
                    DW_DLV_OK) {
                    // If we have a signature it means the type is defined
                    // in .debug_types, so we need to load the DIE pointed
                    // at by the signature and resolve it
                    if (has_attr) {
                        std::string type =
                            get_type_by_signature(fobj.dwarf_handle.get(), die);
                        if (context.is_const)
                            type.insert(0, "const ");

                        if (!context.text.empty())
                            context.text.insert(0, " ");
                        context.text.insert(0, type);
                    }

                    // Treat enums like typedefs, and skip printing its
                    // base type
                    context.is_typedef = (tag == DW_TAG_enumeration_type);
                }
                break;
            case DW_TAG_const_type:
                next_type_is_const = true;
                break;
            case DW_TAG_pointer_type:
                context.text.insert(0, "*");
                break;
            case DW_TAG_reference_type:
                context.text.insert(0, "&");
                break;
            case DW_TAG_restrict_type:
                context.text.insert(0, "restrict ");
                break;
            case DW_TAG_rvalue_reference_type:
                context.text.insert(0, "&&");
                break;
            case DW_TAG_volatile_type:
                context.text.insert(0, "volatile ");
                break;
            case DW_TAG_typedef:
                // Propagate the const-ness to the next type
                // as typedefs are linked to its base type
                next_type_is_const = context.is_const;
                context.is_typedef = true;
                context.has_type = true;
                break;
            case DW_TAG_base_type:
                context.has_type = true;
                break;
            case DW_TAG_formal_parameter:
                context.has_name = true;
                break;
            default:
                is_keyword = false;
                break;
            }
        }

        if (!is_keyword && context.is_const) {
            context.text.insert(0, "const ");
        }

        context.is_const = next_type_is_const;

        Dwarf_Die ref =
            get_referenced_die(fobj.dwarf_handle.get(), die, DW_AT_type, true);
        if (ref) {
            set_parameter_string(fobj, ref, context);
            dwarf_dealloc(fobj.dwarf_handle.get(), ref, DW_DLA_DIE);
        }

        if (!context.has_type && context.has_name) {
            context.text.insert(0, "void ");
            context.has_type = true;
        }
    }

    // Resolve the function return type and parameters
    static void set_function_parameters(std::string &function_name,
                                        std::vector<std::string> &ns,
                                        dwarf_fileobject &fobj, Dwarf_Die die) {
        Dwarf_Debug dwarf = fobj.dwarf_handle.get();
        Dwarf_Error error = DW_DLE_NE;
        Dwarf_Die current_die = 0;
        std::string parameters;
        bool has_spec = true;
        // Check if we have a spec DIE. If we do we use it as it contains
        // more information, like parameter names.
        Dwarf_Die spec_die = get_spec_die(fobj, die);
        if (!spec_die) {
            has_spec = false;
            spec_die = die;
        }

        std::vector<std::string>::const_iterator it = ns.begin();
        std::string ns_name;
        for (it = ns.begin(); it < ns.end(); ++it) {
            ns_name.append(*it).append("::");
        }

        if (!ns_name.empty()) {
            function_name.insert(0, ns_name);
        }

        // See if we have a function return type. It can be either on the
        // current die or in its spec one (usually true for inlined functions)
        std::string return_type =
            get_referenced_die_name(dwarf, die, DW_AT_type, true);
        if (return_type.empty()) {
            return_type =
                get_referenced_die_name(dwarf, spec_die, DW_AT_type, true);
        }
        if (!return_type.empty()) {
            return_type.append(" ");
            function_name.insert(0, return_type);
        }

        if (dwarf_child(spec_die, &current_die, &error) == DW_DLV_OK) {
            for (;;) {
                Dwarf_Die sibling_die = 0;

                Dwarf_Half tag_value;
                dwarf_tag(current_die, &tag_value, &error);

                if (tag_value == DW_TAG_formal_parameter) {
                    // Ignore artificial (ie, compiler generated) parameters
                    bool is_artificial = false;
                    Dwarf_Attribute attr_mem;
                    if (dwarf_attr(current_die, DW_AT_artificial, &attr_mem,
                                   &error) == DW_DLV_OK) {
                        Dwarf_Bool flag = 0;
                        if (dwarf_formflag(attr_mem, &flag, &error) ==
                            DW_DLV_OK) {
                            is_artificial = flag != 0;
                        }
                        dwarf_dealloc(dwarf, attr_mem, DW_DLA_ATTR);
                    }

                    if (!is_artificial) {
                        type_context_t context;
                        set_parameter_string(fobj, current_die, context);

                        if (parameters.empty()) {
                            parameters.append("(");
                        } else {
                            parameters.append(", ");
                        }
                        parameters.append(context.text);
                    }
                }

                int result =
                    dwarf_siblingof(dwarf, current_die, &sibling_die, &error);
                if (result == DW_DLV_ERROR) {
                    break;
                } else if (result == DW_DLV_NO_ENTRY) {
                    break;
                }

                if (current_die != die) {
                    dwarf_dealloc(dwarf, current_die, DW_DLA_DIE);
                    current_die = 0;
                }

                current_die = sibling_die;
            }
        }
        if (parameters.empty())
            parameters = "(";
        parameters.append(")");

        // If we got a spec DIE we need to deallocate it
        if (has_spec)
            dwarf_dealloc(dwarf, spec_die, DW_DLA_DIE);

        function_name.append(parameters);
    }

    // defined here because in C++98, template function cannot take locally
    // defined types... grrr.
    struct inliners_search_cb {
        void operator()(Dwarf_Die die, std::vector<std::string> &ns) {
            Dwarf_Error error = DW_DLE_NE;
            Dwarf_Half tag_value;
            Dwarf_Attribute attr_mem;
            Dwarf_Debug dwarf = fobj.dwarf_handle.get();

            dwarf_tag(die, &tag_value, &error);

            switch (tag_value) {
                char *name;
            case DW_TAG_subprogram:
                if (!trace.source.function.empty())
                    break;
                if (dwarf_diename(die, &name, &error) == DW_DLV_OK) {
                    trace.source.function = std::string(name);
                    dwarf_dealloc(dwarf, name, DW_DLA_STRING);
                } else {
                    // We don't have a function name in this DIE.
                    // Check if there is a referenced non-defining
                    // declaration.
                    trace.source.function = get_referenced_die_name(
                        dwarf, die, DW_AT_abstract_origin, true);
                    if (trace.source.function.empty()) {
                        trace.source.function = get_referenced_die_name(
                            dwarf, die, DW_AT_specification, true);
                    }
                }

                // Append the function parameters, if available
                set_function_parameters(trace.source.function, ns, fobj, die);

                // If the object function name is empty, it's possible that
                // there is no dynamic symbol table (maybe the executable
                // was stripped or not built with -rdynamic). See if we have
                // a DWARF linkage name to use instead. We try both
                // linkage_name and MIPS_linkage_name because the MIPS tag
                // was the unofficial one until it was adopted in DWARF4.
                // Old gcc versions generate MIPS_linkage_name
                if (trace.object_function.empty()) {
                    details::demangler demangler;

                    if (dwarf_attr(die, DW_AT_linkage_name, &attr_mem,
                                   &error) != DW_DLV_OK) {
                        if (dwarf_attr(die, DW_AT_MIPS_linkage_name, &attr_mem,
                                       &error) != DW_DLV_OK) {
                            break;
                        }
                    }

                    char *linkage;
                    if (dwarf_formstring(attr_mem, &linkage, &error) ==
                        DW_DLV_OK) {
                        trace.object_function = demangler.demangle(linkage);
                        dwarf_dealloc(dwarf, linkage, DW_DLA_STRING);
                    }
                    dwarf_dealloc(dwarf, attr_mem, DW_DLA_ATTR);
                }
                break;

            case DW_TAG_inlined_subroutine:
                ResolvedTrace::SourceLoc sloc;

                if (dwarf_diename(die, &name, &error) == DW_DLV_OK) {
                    sloc.function = std::string(name);
                    dwarf_dealloc(dwarf, name, DW_DLA_STRING);
                } else {
                    // We don't have a name for this inlined DIE, it could
                    // be that there is an abstract origin instead.
                    // Get the DW_AT_abstract_origin value, which is a
                    // reference to the source DIE and try to get its name
                    sloc.function = get_referenced_die_name(
                        dwarf, die, DW_AT_abstract_origin, true);
                }

                set_function_parameters(sloc.function, ns, fobj, die);

                std::string file = die_call_file(dwarf, die, cu_die);
                if (!file.empty())
                    sloc.filename = file;

                Dwarf_Unsigned number = 0;
                if (dwarf_attr(die, DW_AT_call_line, &attr_mem, &error) ==
                    DW_DLV_OK) {
                    if (dwarf_formudata(attr_mem, &number, &error) ==
                        DW_DLV_OK) {
                        sloc.line = number;
                    }
                    dwarf_dealloc(dwarf, attr_mem, DW_DLA_ATTR);
                }

                if (dwarf_attr(die, DW_AT_call_column, &attr_mem, &error) ==
                    DW_DLV_OK) {
                    if (dwarf_formudata(attr_mem, &number, &error) ==
                        DW_DLV_OK) {
                        sloc.col = number;
                    }
                    dwarf_dealloc(dwarf, attr_mem, DW_DLA_ATTR);
                }

                trace.inliners.push_back(sloc);
                break;
            };
        }
        ResolvedTrace &trace;
        dwarf_fileobject &fobj;
        Dwarf_Die cu_die;
        inliners_search_cb(ResolvedTrace &t, dwarf_fileobject &f, Dwarf_Die c)
            : trace(t), fobj(f), cu_die(c) {}
    };

    static Dwarf_Die find_fundie_by_pc(dwarf_fileobject &fobj,
                                       Dwarf_Die parent_die, Dwarf_Addr pc,
                                       Dwarf_Die result) {
        Dwarf_Die current_die = 0;
        Dwarf_Error error = DW_DLE_NE;
        Dwarf_Debug dwarf = fobj.dwarf_handle.get();

        if (dwarf_child(parent_die, &current_die, &error) != DW_DLV_OK) {
            return NULL;
        }

        for (;;) {
            Dwarf_Die sibling_die = 0;
            Dwarf_Half tag_value;
            dwarf_tag(current_die, &tag_value, &error);

            switch (tag_value) {
            case DW_TAG_subprogram:
            case DW_TAG_inlined_subroutine:
                if (die_has_pc(fobj, current_die, pc)) {
                    return current_die;
                }
            };
            bool declaration = false;
            Dwarf_Attribute attr_mem;
            if (dwarf_attr(current_die, DW_AT_declaration, &attr_mem, &error) ==
                DW_DLV_OK) {
                Dwarf_Bool flag = 0;
                if (dwarf_formflag(attr_mem, &flag, &error) == DW_DLV_OK) {
                    declaration = flag != 0;
                }
                dwarf_dealloc(dwarf, attr_mem, DW_DLA_ATTR);
            }

            if (!declaration) {
                // let's be curious and look deeper in the tree, functions are
                // not necessarily at the first level, but might be nested
                // inside a namespace, structure, a function, an inlined
                // function etc.
                Dwarf_Die die_mem = 0;
                Dwarf_Die indie =
                    find_fundie_by_pc(fobj, current_die, pc, die_mem);
                if (indie) {
                    result = die_mem;
                    return result;
                }
            }

            int res = dwarf_siblingof(dwarf, current_die, &sibling_die, &error);
            if (res == DW_DLV_ERROR) {
                return NULL;
            } else if (res == DW_DLV_NO_ENTRY) {
                break;
            }

            if (current_die != parent_die) {
                dwarf_dealloc(dwarf, current_die, DW_DLA_DIE);
                current_die = 0;
            }

            current_die = sibling_die;
        }
        return NULL;
    }

    template <typename CB>
    static bool deep_first_search_by_pc(dwarf_fileobject &fobj,
                                        Dwarf_Die parent_die, Dwarf_Addr pc,
                                        std::vector<std::string> &ns, CB cb) {
        Dwarf_Die current_die = 0;
        Dwarf_Debug dwarf = fobj.dwarf_handle.get();
        Dwarf_Error error = DW_DLE_NE;

        if (dwarf_child(parent_die, &current_die, &error) != DW_DLV_OK) {
            return false;
        }

        bool branch_has_pc = false;
        bool has_namespace = false;
        for (;;) {
            Dwarf_Die sibling_die = 0;

            Dwarf_Half tag;
            if (dwarf_tag(current_die, &tag, &error) == DW_DLV_OK) {
                if (tag == DW_TAG_namespace || tag == DW_TAG_class_type) {
                    char *ns_name = NULL;
                    if (dwarf_diename(current_die, &ns_name, &error) ==
                        DW_DLV_OK) {
                        if (ns_name) {
                            ns.push_back(std::string(ns_name));
                        } else {
                            ns.push_back("<unknown>");
                        }
                        dwarf_dealloc(dwarf, ns_name, DW_DLA_STRING);
                    } else {
                        ns.push_back("<unknown>");
                    }
                    has_namespace = true;
                }
            }

            bool declaration = false;
            Dwarf_Attribute attr_mem;
            if (tag != DW_TAG_class_type &&
                dwarf_attr(current_die, DW_AT_declaration, &attr_mem, &error) ==
                    DW_DLV_OK) {
                Dwarf_Bool flag = 0;
                if (dwarf_formflag(attr_mem, &flag, &error) == DW_DLV_OK) {
                    declaration = flag != 0;
                }
                dwarf_dealloc(dwarf, attr_mem, DW_DLA_ATTR);
            }

            if (!declaration) {
                // let's be curious and look deeper in the tree, function are
                // not necessarily at the first level, but might be nested
                // inside a namespace, structure, a function, an inlined
                // function etc.
                branch_has_pc =
                    deep_first_search_by_pc(fobj, current_die, pc, ns, cb);
            }

            if (!branch_has_pc) {
                branch_has_pc = die_has_pc(fobj, current_die, pc);
            }

            if (branch_has_pc) {
                cb(current_die, ns);
            }

            int result =
                dwarf_siblingof(dwarf, current_die, &sibling_die, &error);
            if (result == DW_DLV_ERROR) {
                return false;
            } else if (result == DW_DLV_NO_ENTRY) {
                break;
            }

            if (current_die != parent_die) {
                dwarf_dealloc(dwarf, current_die, DW_DLA_DIE);
                current_die = 0;
            }

            if (has_namespace) {
                has_namespace = false;
                ns.pop_back();
            }
            current_die = sibling_die;
        }

        if (has_namespace) {
            ns.pop_back();
        }
        return branch_has_pc;
    }

    static std::string die_call_file(Dwarf_Debug dwarf, Dwarf_Die die,
                                     Dwarf_Die cu_die) {
        Dwarf_Attribute attr_mem;
        Dwarf_Error error = DW_DLE_NE;
        Dwarf_Unsigned file_index;

        std::string file;

        if (dwarf_attr(die, DW_AT_call_file, &attr_mem, &error) == DW_DLV_OK) {
            if (dwarf_formudata(attr_mem, &file_index, &error) != DW_DLV_OK) {
                file_index = 0;
            }
            dwarf_dealloc(dwarf, attr_mem, DW_DLA_ATTR);

            if (file_index == 0) {
                return file;
            }

            char **srcfiles = 0;
            Dwarf_Signed file_count = 0;
            if (dwarf_srcfiles(cu_die, &srcfiles, &file_count, &error) ==
                DW_DLV_OK) {
                if (file_count > 0 &&
                    file_index <= static_cast<Dwarf_Unsigned>(file_count)) {
                    file = std::string(srcfiles[file_index - 1]);
                }

                // Deallocate all strings!
                for (int i = 0; i < file_count; ++i) {
                    dwarf_dealloc(dwarf, srcfiles[i], DW_DLA_STRING);
                }
                dwarf_dealloc(dwarf, srcfiles, DW_DLA_LIST);
            }
        }
        return file;
    }

    Dwarf_Die find_die(dwarf_fileobject &fobj, Dwarf_Addr addr) {
        // Let's get to work! First see if we have a debug_aranges section so
        // we can speed up the search

        Dwarf_Debug dwarf = fobj.dwarf_handle.get();
        Dwarf_Error error = DW_DLE_NE;
        Dwarf_Arange *aranges;
        Dwarf_Signed arange_count;

        Dwarf_Die returnDie;
        bool found = false;
        if (dwarf_get_aranges(dwarf, &aranges, &arange_count, &error) !=
            DW_DLV_OK) {
            aranges = NULL;
        }

        if (aranges) {
            // We have aranges. Get the one where our address is.
            Dwarf_Arange arange;
            if (dwarf_get_arange(aranges, arange_count, addr, &arange,
                                 &error) == DW_DLV_OK) {

                // We found our address. Get the compilation-unit DIE offset
                // represented by the given address range.
                Dwarf_Off cu_die_offset;
                if (dwarf_get_cu_die_offset(arange, &cu_die_offset, &error) ==
                    DW_DLV_OK) {
                    // Get the DIE at the offset returned by the aranges search.
                    // We set is_info to 1 to specify that the offset is from
                    // the .debug_info section (and not .debug_types)
                    int dwarf_result = dwarf_offdie_b(dwarf, cu_die_offset, 1,
                                                      &returnDie, &error);

                    found = dwarf_result == DW_DLV_OK;
                }
                dwarf_dealloc(dwarf, arange, DW_DLA_ARANGE);
            }
        }

        if (found)
            return returnDie; // The caller is responsible for freeing the die

        // The search for aranges failed. Try to find our address by scanning
        // all compilation units.
        Dwarf_Unsigned next_cu_header;
        Dwarf_Half tag = 0;
        returnDie = 0;

        while (!found && dwarf_next_cu_header_d(dwarf, 1, 0, 0, 0, 0, 0, 0, 0,
                                                0, &next_cu_header, 0,
                                                &error) == DW_DLV_OK) {

            if (returnDie)
                dwarf_dealloc(dwarf, returnDie, DW_DLA_DIE);

            if (dwarf_siblingof(dwarf, 0, &returnDie, &error) == DW_DLV_OK) {
                if ((dwarf_tag(returnDie, &tag, &error) == DW_DLV_OK) &&
                    tag == DW_TAG_compile_unit) {
                    if (die_has_pc(fobj, returnDie, addr)) {
                        found = true;
                    }
                }
            }
        }

        if (found) {
            while (dwarf_next_cu_header_d(dwarf, 1, 0, 0, 0, 0, 0, 0, 0, 0,
                                          &next_cu_header, 0,
                                          &error) == DW_DLV_OK) {
                // Reset the cu header state. Libdwarf's next_cu_header API
                // keeps its own iterator per Dwarf_Debug that can't be reset.
                // We need to keep fetching elements until the end.
            }
        }

        if (found)
            return returnDie;

        // We couldn't find any compilation units with ranges or a high/low pc.
        // Try again by looking at all DIEs in all compilation units.
        Dwarf_Die cudie;
        while (dwarf_next_cu_header_d(dwarf, 1, 0, 0, 0, 0, 0, 0, 0, 0,
                                      &next_cu_header, 0,
                                      &error) == DW_DLV_OK) {
            if (dwarf_siblingof(dwarf, 0, &cudie, &error) == DW_DLV_OK) {
                Dwarf_Die die_mem = 0;
                Dwarf_Die resultDie =
                    find_fundie_by_pc(fobj, cudie, addr, die_mem);

                if (resultDie) {
                    found = true;
                    break;
                }
            }
        }

        if (found) {
            while (dwarf_next_cu_header_d(dwarf, 1, 0, 0, 0, 0, 0, 0, 0, 0,
                                          &next_cu_header, 0,
                                          &error) == DW_DLV_OK) {
                // Reset the cu header state. Libdwarf's next_cu_header API
                // keeps its own iterator per Dwarf_Debug that can't be reset.
                // We need to keep fetching elements until the end.
            }
        }

        if (found)
            return cudie;

        // We failed.
        return NULL;
    }
};
#endif // BACKWARD_HAS_DWARF == 1

template <>
class TraceResolverImpl<system_tag::linux_tag>
    : public TraceResolverLinuxImpl<trace_resolver_tag::current> {};

#endif // BACKWARD_SYSTEM_LINUX

#ifdef BACKWARD_SYSTEM_DARWIN

template <typename STACKTRACE_TAG> class TraceResolverDarwinImpl;

template <>
class TraceResolverDarwinImpl<trace_resolver_tag::backtrace_symbol>
    : public TraceResolverImplBase {
  public:
    void load_addresses(void *const *addresses, int address_count) override {
        if (address_count == 0) {
            return;
        }
        _symbols.reset(backtrace_symbols(addresses, address_count));
    }

    ResolvedTrace resolve(ResolvedTrace trace) override {
        // parse:
        // <n>  <file>  <addr>  <mangled-name> + <offset>
        char *filename = _symbols[trace.idx];

        // skip "<n>  "
        while (*filename && *filename != ' ')
            filename++;
        while (*filename == ' ')
            filename++;

        // find start of <mangled-name> from end (<file> may contain a space)
        char *p = filename + strlen(filename) - 1;
        // skip to start of " + <offset>"
        while (p > filename && *p != ' ')
            p--;
        while (p > filename && *p == ' ')
            p--;
        while (p > filename && *p != ' ')
            p--;
        while (p > filename && *p == ' ')
            p--;
        char *funcname_end = p + 1;

        // skip to start of "<manged-name>"
        while (p > filename && *p != ' ')
            p--;
        char *funcname = p + 1;

        // skip to start of "  <addr>  "
        while (p > filename && *p == ' ')
            p--;
        while (p > filename && *p != ' ')
            p--;
        while (p > filename && *p == ' ')
            p--;

        // skip "<file>", handling the case where it contains a
        char *filename_end = p + 1;
        if (p == filename) {
            // something went wrong, give up
            filename_end = filename + strlen(filename);
            funcname = filename_end;
        }
        trace.object_filename.assign(
            filename, filename_end); // ok even if filename_end is the ending \0
                                     // (then we assign entire string)

        if (*funcname) { // if it's not end of string
            *funcname_end = '\0';

            trace.object_function = this->demangle(funcname);
            trace.object_function += " ";
            trace.object_function += (funcname_end + 1);
            trace.source.function =
                trace.object_function; // we cannot do better.
        }
        return trace;
    }

  private:
    details::handle<char **> _symbols;
};

template <>
class TraceResolverImpl<system_tag::darwin_tag>
    : public TraceResolverDarwinImpl<trace_resolver_tag::current> {};

#endif // BACKWARD_SYSTEM_DARWIN

#ifdef BACKWARD_SYSTEM_WINDOWS

// Load all symbol info
// Based on:
// https://stackoverflow.com/questions/6205981/windows-c-stack-trace-from-a-running-app/28276227#28276227

struct module_data {
    std::string image_name;
    std::string module_name;
    void *base_address;
    DWORD load_size;
};

class get_mod_info {
    HANDLE process;
    static const int buffer_length = 4096;

  public:
    get_mod_info(HANDLE h) : process(h) {}

    module_data operator()(HMODULE module) {
        module_data ret;
        char temp[buffer_length];
        MODULEINFO mi;

        GetModuleInformation(process, module, &mi, sizeof(mi));
        ret.base_address = mi.lpBaseOfDll;
        ret.load_size = mi.SizeOfImage;

        GetModuleFileNameExA(process, module, temp, sizeof(temp));
        ret.image_name = temp;
        GetModuleBaseNameA(process, module, temp, sizeof(temp));
        ret.module_name = temp;
        std::vector<char> img(ret.image_name.begin(), ret.image_name.end());
        std::vector<char> mod(ret.module_name.begin(), ret.module_name.end());
        SymLoadModule64(process, 0, &img[0], &mod[0], (DWORD64)ret.base_address,
                        ret.load_size);
        return ret;
    }
};

template <>
class TraceResolverImpl<system_tag::windows_tag>
    : public TraceResolverImplBase {
  public:
    TraceResolverImpl() {

        HANDLE process = GetCurrentProcess();

        std::vector<module_data> modules;
        DWORD cbNeeded;
        std::vector<HMODULE> module_handles(1);
        SymInitialize(process, NULL, false);
        DWORD symOptions = SymGetOptions();
        symOptions |= SYMOPT_LOAD_LINES | SYMOPT_UNDNAME;
        SymSetOptions(symOptions);
        EnumProcessModules(
            process, &module_handles[0],
            static_cast<DWORD>(module_handles.size() * sizeof(HMODULE)),
            &cbNeeded);
        module_handles.resize(cbNeeded / sizeof(HMODULE));
        EnumProcessModules(
            process, &module_handles[0],
            static_cast<DWORD>(module_handles.size() * sizeof(HMODULE)),
            &cbNeeded);
        std::transform(module_handles.begin(), module_handles.end(),
                       std::back_inserter(modules), get_mod_info(process));
        void *base = modules[0].base_address;
        IMAGE_NT_HEADERS *h = ImageNtHeader(base);
        image_type = h->FileHeader.Machine;
    }

    static const int max_sym_len = 255;
    struct symbol_t {
        SYMBOL_INFO sym;
        char buffer[max_sym_len];
    } sym;

    DWORD64 displacement;

    ResolvedTrace resolve(ResolvedTrace t) override {
        HANDLE process = GetCurrentProcess();

        char name[256];

        memset(&sym, 0, sizeof(sym));
        sym.sym.SizeOfStruct = sizeof(SYMBOL_INFO);
        sym.sym.MaxNameLen = max_sym_len;

        if (!SymFromAddr(process, (ULONG64)t.addr, &displacement, &sym.sym)) {
            // TODO:  error handling everywhere
            char *lpMsgBuf;
            DWORD dw = GetLastError();

            if (FormatMessageA(FORMAT_MESSAGE_ALLOCATE_BUFFER |
                                   FORMAT_MESSAGE_FROM_SYSTEM |
                                   FORMAT_MESSAGE_IGNORE_INSERTS,
                               NULL, dw,
                               MAKELANGID(LANG_NEUTRAL, SUBLANG_DEFAULT),
                               (char *)&lpMsgBuf, 0, NULL)) {
                std::fprintf(stderr, "%s\n", lpMsgBuf);
                LocalFree(lpMsgBuf);
            }

            // abort();
        }
        UnDecorateSymbolName(sym.sym.Name, (PSTR)name, 256, UNDNAME_COMPLETE);

        DWORD offset = 0;
        IMAGEHLP_LINE line;
        if (SymGetLineFromAddr(process, (ULONG64)t.addr, &offset, &line)) {
            t.object_filename = line.FileName;
            t.source.filename = line.FileName;
            t.source.line = line.LineNumber;
            t.source.col = offset;
        }

        t.source.function = name;
        t.object_filename = "";
        t.object_function = name;

        return t;
    }

    DWORD machine_type() const { return image_type; }

  private:
    DWORD image_type;
};

#endif

class TraceResolver : public TraceResolverImpl<system_tag::current_tag> {};

/*************** CODE SNIPPET ***************/

class SourceFile {
  public:
    typedef std::vector<std::pair<unsigned, std::string>> lines_t;

    SourceFile() {}
    SourceFile(const std::string &path) {
        // 1. If BACKWARD_CXX_SOURCE_PREFIXES is set then assume it contains
        //    a colon-separated list of path prefixes.  Try prepending each
        //    to the given path until a valid file is found.
        const std::vector<std::string> &prefixes =
            get_paths_from_env_variable();
        for (size_t i = 0; i < prefixes.size(); ++i) {
            // Double slashes (//) should not be a problem.
            std::string new_path = prefixes[i] + '/' + path;
            _file.reset(new std::ifstream(new_path.c_str()));
            if (is_open())
                break;
        }
        // 2. If no valid file found then fallback to opening the path as-is.
        if (!_file || !is_open()) {
            _file.reset(new std::ifstream(path.c_str()));
        }
    }
    bool is_open() const { return _file->is_open(); }

    lines_t &get_lines(unsigned line_start, unsigned line_count,
                       lines_t &lines) {
        using namespace std;
        // This function make uses of the dumbest algo ever:
        //	1) seek(0)
        //	2) read lines one by one and discard until line_start
        //	3) read line one by one until line_start + line_count
        //
        // If you are getting snippets many time from the same file, it is
        // somewhat a waste of CPU, feel free to benchmark and propose a
        // better solution ;)

        _file->clear();
        _file->seekg(0);
        string line;
        unsigned line_idx;

        for (line_idx = 1; line_idx < line_start; ++line_idx) {
            std::getline(*_file, line);
            if (!*_file) {
                return lines;
            }
        }

        // think of it like a lambda in C++98 ;)
        // but look, I will reuse it two times!
        // What a good boy am I.
        struct isspace {
            bool operator()(char c) { return std::isspace(c); }
        };

        bool started = false;
        for (; line_idx < line_start + line_count; ++line_idx) {
            getline(*_file, line);
            if (!*_file) {
                return lines;
            }
            if (!started) {
                if (std::find_if(line.begin(), line.end(), not_isspace()) ==
                    line.end())
                    continue;
                started = true;
            }
            lines.push_back(make_pair(line_idx, line));
        }

        lines.erase(
            std::find_if(lines.rbegin(), lines.rend(), not_isempty()).base(),
            lines.end());
        return lines;
    }

    lines_t get_lines(unsigned line_start, unsigned line_count) {
        lines_t lines;
        return get_lines(line_start, line_count, lines);
    }

    // there is no find_if_not in C++98, lets do something crappy to
    // workaround.
    struct not_isspace {
        bool operator()(char c) { return !std::isspace(c); }
    };
    // and define this one here because C++98 is not happy with local defined
    // struct passed to template functions, fuuuu.
    struct not_isempty {
        bool operator()(const lines_t::value_type &p) {
            return !(std::find_if(p.second.begin(), p.second.end(),
                                  not_isspace()) == p.second.end());
        }
    };

    void swap(SourceFile &b) { _file.swap(b._file); }

#ifdef BACKWARD_ATLEAST_CXX11
    SourceFile(SourceFile &&from) : _file(nullptr) { swap(from); }
    SourceFile &operator=(SourceFile &&from) {
        swap(from);
        return *this;
    }
#else
    explicit SourceFile(const SourceFile &from) {
        // some sort of poor man's move semantic.
        swap(const_cast<SourceFile &>(from));
    }
    SourceFile &operator=(const SourceFile &from) {
        // some sort of poor man's move semantic.
        swap(const_cast<SourceFile &>(from));
        return *this;
    }
#endif

    // Allow adding to paths gotten from BACKWARD_CXX_SOURCE_PREFIXES after
    // loading the library; this can be useful when the library is loaded when
    // the locations are unknown Warning: Because this edits the static paths
    // variable, it is *not* intrinsiclly thread safe
    static void add_paths_to_env_variable_impl(const std::string &to_add) {
        get_mutable_paths_from_env_variable().push_back(to_add);
    }

  private:
    details::handle<std::ifstream *, details::default_delete<std::ifstream *>>
        _file;

    static std::vector<std::string> get_paths_from_env_variable_impl() {
        std::vector<std::string> paths;
        const char *prefixes_str = std::getenv("BACKWARD_CXX_SOURCE_PREFIXES");
        if (prefixes_str && prefixes_str[0]) {
            paths = details::split_source_prefixes(prefixes_str);
        }
        return paths;
    }

    static std::vector<std::string> &get_mutable_paths_from_env_variable() {
        static volatile std::vector<std::string> paths =
            get_paths_from_env_variable_impl();
        return const_cast<std::vector<std::string> &>(paths);
    }

    static const std::vector<std::string> &get_paths_from_env_variable() {
        return get_mutable_paths_from_env_variable();
    }

#ifdef BACKWARD_ATLEAST_CXX11
    SourceFile(const SourceFile &) = delete;
    SourceFile &operator=(const SourceFile &) = delete;
#endif
};

class SnippetFactory {
  public:
    typedef SourceFile::lines_t lines_t;

    lines_t get_snippet(const std::string &filename, unsigned line_start,
                        unsigned context_size) {

        SourceFile &src_file = get_src_file(filename);
        unsigned start = line_start - context_size / 2;
        return src_file.get_lines(start, context_size);
    }

    lines_t get_combined_snippet(const std::string &filename_a, unsigned line_a,
                                 const std::string &filename_b, unsigned line_b,
                                 unsigned context_size) {
        SourceFile &src_file_a = get_src_file(filename_a);
        SourceFile &src_file_b = get_src_file(filename_b);

        lines_t lines =
            src_file_a.get_lines(line_a - context_size / 4, context_size / 2);
        src_file_b.get_lines(line_b - context_size / 4, context_size / 2,
                             lines);
        return lines;
    }

    lines_t get_coalesced_snippet(const std::string &filename, unsigned line_a,
                                  unsigned line_b, unsigned context_size) {
        SourceFile &src_file = get_src_file(filename);

        using std::max;
        using std::min;
        unsigned a = min(line_a, line_b);
        unsigned b = max(line_a, line_b);

        if ((b - a) < (context_size / 3)) {
            return src_file.get_lines((a + b - context_size + 1) / 2,
                                      context_size);
        }

        lines_t lines =
            src_file.get_lines(a - context_size / 4, context_size / 2);
        src_file.get_lines(b - context_size / 4, context_size / 2, lines);
        return lines;
    }

  private:
    typedef details::hashtable<std::string, SourceFile>::type src_files_t;
    src_files_t _src_files;

    SourceFile &get_src_file(const std::string &filename) {
        src_files_t::iterator it = _src_files.find(filename);
        if (it != _src_files.end()) {
            return it->second;
        }
        SourceFile &new_src_file = _src_files[filename];
        new_src_file = SourceFile(filename);
        return new_src_file;
    }
};

/*************** PRINTER ***************/

namespace ColorMode {
enum type { automatic, never, always };
}

class cfile_streambuf : public std::streambuf {
  public:
    cfile_streambuf(FILE *_sink) : sink(_sink) {}
    int_type underflow() override { return traits_type::eof(); }
    int_type overflow(int_type ch) override {
        if (traits_type::not_eof(ch) && fputc(ch, sink) != EOF) {
            return ch;
        }
        return traits_type::eof();
    }

    std::streamsize xsputn(const char_type *s, std::streamsize count) override {
        return static_cast<std::streamsize>(
            fwrite(s, sizeof *s, static_cast<size_t>(count), sink));
    }

#ifdef BACKWARD_ATLEAST_CXX11
  public:
    cfile_streambuf(const cfile_streambuf &) = delete;
    cfile_streambuf &operator=(const cfile_streambuf &) = delete;
#else
  private:
    cfile_streambuf(const cfile_streambuf &);
    cfile_streambuf &operator=(const cfile_streambuf &);
#endif

  private:
    FILE *sink;
    std::vector<char> buffer;
};

#ifdef BACKWARD_SYSTEM_LINUX

namespace Color {
enum type { yellow = 33, purple = 35, reset = 39 };
} // namespace Color

class Colorize {
  public:
    Colorize(std::ostream &os) : _os(os), _reset(false), _enabled(false) {}

    void activate(ColorMode::type mode) {
        _enabled = mode == ColorMode::always;
    }

    void activate(ColorMode::type mode, FILE *fp) {
        activate(mode, fileno(fp));
    }

    void set_color(Color::type ccode) {
        if (!_enabled)
            return;

        // I assume that the terminal can handle basic colors. Seriously I
        // don't want to deal with all the termcap shit.
        _os << "\033[" << static_cast<int>(ccode) << "m";
        _reset = (ccode != Color::reset);
    }

    ~Colorize() {
        if (_reset) {
            set_color(Color::reset);
        }
    }

  private:
    void activate(ColorMode::type mode, int fd) {
        activate(mode == ColorMode::automatic && isatty(fd) ? ColorMode::always
                                                            : mode);
    }

    std::ostream &_os;
    bool _reset;
    bool _enabled;
};

#else // ndef BACKWARD_SYSTEM_LINUX

namespace Color {
enum type { yellow = 0, purple = 0, reset = 0 };
} // namespace Color

class Colorize {
  public:
    Colorize(std::ostream &) {}
    void activate(ColorMode::type) {}
    void activate(ColorMode::type, FILE *) {}
    void set_color(Color::type) {}
};

#endif // BACKWARD_SYSTEM_LINUX

class Printer {
  public:
    bool snippet;
    ColorMode::type color_mode;
    bool address;
    bool object;
    int inliner_context_size;
    int trace_context_size;
    bool reverse;

    Printer()
        : snippet(true), color_mode(ColorMode::automatic), address(false),
          object(false), inliner_context_size(5), trace_context_size(7),
          reverse(true) {}

    template <typename ST> FILE *print(ST &st, FILE *fp = stderr) {
        cfile_streambuf obuf(fp);
        std::ostream os(&obuf);
        Colorize colorize(os);
        colorize.activate(color_mode, fp);
        print_stacktrace(st, os, colorize);
        return fp;
    }

    template <typename ST> std::ostream &print(ST &st, std::ostream &os) {
        Colorize colorize(os);
        colorize.activate(color_mode);
        print_stacktrace(st, os, colorize);
        return os;
    }

    template <typename IT>
    FILE *print(IT begin, IT end, FILE *fp = stderr, size_t thread_id = 0) {
        cfile_streambuf obuf(fp);
        std::ostream os(&obuf);
        Colorize colorize(os);
        colorize.activate(color_mode, fp);
        print_stacktrace(begin, end, os, thread_id, colorize);
        return fp;
    }

    template <typename IT>
    std::ostream &print(IT begin, IT end, std::ostream &os,
                        size_t thread_id = 0) {
        Colorize colorize(os);
        colorize.activate(color_mode);
        print_stacktrace(begin, end, os, thread_id, colorize);
        return os;
    }

    TraceResolver const &resolver() const { return _resolver; }

  private:
    TraceResolver _resolver;
    SnippetFactory _snippets;

    template <typename ST>
    void print_stacktrace(ST &st, std::ostream &os, Colorize &colorize) {
        print_header(os, st.thread_id());
        _resolver.load_stacktrace(st);
        if (reverse) {
            for (size_t trace_idx = st.size(); trace_idx > 0; --trace_idx) {
                print_trace(os, _resolver.resolve(st[trace_idx - 1]), colorize);
            }
        } else {
            for (size_t trace_idx = 0; trace_idx < st.size(); ++trace_idx) {
                print_trace(os, _resolver.resolve(st[trace_idx]), colorize);
            }
        }
    }

    template <typename IT>
    void print_stacktrace(IT begin, IT end, std::ostream &os, size_t thread_id,
                          Colorize &colorize) {
        print_header(os, thread_id);
        for (; begin != end; ++begin) {
            print_trace(os, *begin, colorize);
        }
    }

    void print_header(std::ostream &os, size_t thread_id) {
        os << "Stack trace (most recent call last)";
        if (thread_id) {
            os << " in thread " << thread_id;
        }
        os << ":\n";
    }

    void print_trace(std::ostream &os, const ResolvedTrace &trace,
                     Colorize &colorize) {
        os << "#" << std::left << std::setw(2) << trace.idx << std::right;
        bool already_indented = true;

        if (!trace.source.filename.size() || object) {
            os << "   Object \"" << trace.object_filename << "\", at "
               << trace.addr << ", in " << trace.object_function << "\n";
            already_indented = false;
        }

        for (size_t inliner_idx = trace.inliners.size(); inliner_idx > 0;
             --inliner_idx) {
            if (!already_indented) {
                os << "   ";
            }
            const ResolvedTrace::SourceLoc &inliner_loc =
                trace.inliners[inliner_idx - 1];
            print_source_loc(os, " | ", inliner_loc);
            if (snippet) {
                print_snippet(os, "    | ", inliner_loc, colorize,
                              Color::purple, inliner_context_size);
            }
            already_indented = false;
        }

        if (trace.source.filename.size()) {
            if (!already_indented) {
                os << "   ";
            }
            print_source_loc(os, "   ", trace.source, trace.addr);
            if (snippet) {
                print_snippet(os, "      ", trace.source, colorize,
                              Color::yellow, trace_context_size);
            }
        }
    }

    void print_snippet(std::ostream &os, const char *indent,
                       const ResolvedTrace::SourceLoc &source_loc,
                       Colorize &colorize, Color::type color_code,
                       int context_size) {
        using namespace std;
        typedef SnippetFactory::lines_t lines_t;

        lines_t lines =
            _snippets.get_snippet(source_loc.filename, source_loc.line,
                                  static_cast<unsigned>(context_size));

        for (lines_t::const_iterator it = lines.begin(); it != lines.end();
             ++it) {
            if (it->first == source_loc.line) {
                colorize.set_color(color_code);
                os << indent << ">";
            } else {
                os << indent << " ";
            }
            os << std::setw(4) << it->first << ": " << it->second << "\n";
            if (it->first == source_loc.line) {
                colorize.set_color(Color::reset);
            }
        }
    }

    void print_source_loc(std::ostream &os, const char *indent,
                          const ResolvedTrace::SourceLoc &source_loc,
                          void *addr = nullptr) {
        os << indent << "Source \"" << source_loc.filename << "\", line "
           << source_loc.line << ", in " << source_loc.function;

        if (address && addr != nullptr) {
            os << " [" << addr << "]";
        }
        os << "\n";
    }
};

/*************** SIGNALS HANDLING ***************/

#if defined(BACKWARD_SYSTEM_LINUX) || defined(BACKWARD_SYSTEM_DARWIN)

class SignalHandling {
  public:
    static std::vector<int> make_default_signals() {
        const int posix_signals[] = {
            // Signals for which the default action is "Core".
            SIGABRT, // Abort signal from abort(3)
            SIGBUS,  // Bus error (bad memory access)
            SIGFPE,  // Floating point exception
            SIGUSR1, // A la https://github.com/surma/stacksignal
            SIGILL,  // Illegal Instruction
            SIGIOT,  // IOT trap. A synonym for SIGABRT
            SIGQUIT, // Quit from keyboard
            SIGSEGV, // Invalid memory reference
            SIGSYS,  // Bad argument to routine (SVr4)
            SIGTRAP, // Trace/breakpoint trap
            SIGXCPU, // CPU time limit exceeded (4.2BSD)
            SIGXFSZ, // File size limit exceeded (4.2BSD)
#if defined(BACKWARD_SYSTEM_DARWIN)
            SIGEMT, // emulation instruction executed
#endif
        };
        return std::vector<int>(posix_signals,
                                posix_signals + sizeof posix_signals /
                                                    sizeof posix_signals[0]);
    }

    SignalHandling(
        const std::vector<int> &posix_signals = make_default_signals())
        : _loaded(false) {
        bool success = true;

        const size_t stack_size = 1024 * 1024 * 8;
        _stack_content.reset(static_cast<char *>(malloc(stack_size)));
        if (_stack_content) {
            stack_t ss;
            ss.ss_sp = _stack_content.get();
            ss.ss_size = stack_size;
            ss.ss_flags = 0;
            if (sigaltstack(&ss, nullptr) < 0) {
                success = false;
            }
        } else {
            success = false;
        }

        for (size_t i = 0; i < posix_signals.size(); ++i) {
            struct sigaction action;
            memset(&action, 0, sizeof action);
            action.sa_flags = static_cast<int>(SA_SIGINFO | SA_ONSTACK |
                                               SA_NODEFER | SA_RESETHAND);
            sigfillset(&action.sa_mask);
            sigdelset(&action.sa_mask, posix_signals[i]);
#if defined(__clang__)
#pragma clang diagnostic push
#pragma clang diagnostic ignored "-Wdisabled-macro-expansion"
#endif
            action.sa_sigaction = &sig_handler;
#if defined(__clang__)
#pragma clang diagnostic pop
#endif

            int r = sigaction(posix_signals[i], &action, nullptr);
            if (r < 0)
                success = false;
        }

        _loaded = success;
    }

    bool loaded() const { return _loaded; }

    static void handleSignal(int sig, siginfo_t *info, void *_ctx) {
        ucontext_t *uctx = static_cast<ucontext_t *>(_ctx);
        // this cat is completely necessary to this signal handling. if it is
        // removed then the backtraces by themselves are too scary for any mere
        // mortal to withstand
        fprintf(stderr, "          ____\n");
        fprintf(stderr, "        /＞    フ\n");
        fprintf(stderr, "       |  _  _ |\n");
        fprintf(stderr, "      /` ミ_x ノ\n");
        fprintf(stderr, "     /        |\n");
        fprintf(stderr, "    /   ヽ    ﾉ\n");
        fprintf(stderr, "   |     | | |\n");
        fprintf(stderr, "／￣      | | |\n");
        fprintf(stderr, "| (￣ヽ＿ヽ)_)_)\n");
        fprintf(stderr, "＼二つ\n");
        fprintf(stderr, "Segfault cat says: ");
        fprintf(stderr, "process %d received signal:\n> \"%s\"\n", getpid(),
                strsignal(sig));
        fprintf(stderr, "faulting address: %p\n",
                reinterpret_cast<void *>(info->si_addr));
        fflush(stderr);
        StackTrace st;
        void *error_addr = nullptr;
#ifdef REG_RIP // x86_64
        error_addr = reinterpret_cast<void *>(uctx->uc_mcontext.gregs[REG_RIP]);
#elif defined(REG_EIP) // x86_32
        error_addr = reinterpret_cast<void *>(uctx->uc_mcontext.gregs[REG_EIP]);
#elif defined(__arm__)
        error_addr = reinterpret_cast<void *>(uctx->uc_mcontext.arm_pc);
#elif defined(__aarch64__)
#if defined(__APPLE__)
        error_addr = reinterpret_cast<void *>(uctx->uc_mcontext->__ss.__pc);
#else
        error_addr = reinterpret_cast<void *>(uctx->uc_mcontext.pc);
#endif
#elif defined(__mips__)
        error_addr = reinterpret_cast<void *>(
            reinterpret_cast<struct sigcontext *>(&uctx->uc_mcontext)->sc_pc);
#elif defined(__APPLE__) && defined(__POWERPC__)
        error_addr = reinterpret_cast<void *>(uctx->uc_mcontext->__ss.__srr0);
#elif defined(__ppc__) || defined(__powerpc) || defined(__powerpc__) ||        \
    defined(__POWERPC__)
        error_addr = reinterpret_cast<void *>(uctx->uc_mcontext.regs->nip);
#elif defined(__riscv)
        error_addr =
            reinterpret_cast<void *>(uctx->uc_mcontext.__gregs[REG_PC]);
#elif defined(__s390x__)
        error_addr = reinterpret_cast<void *>(uctx->uc_mcontext.psw.addr);
#elif defined(__APPLE__) && defined(__x86_64__)
        error_addr = reinterpret_cast<void *>(uctx->uc_mcontext->__ss.__rip);
#elif defined(__APPLE__)
        error_addr = reinterpret_cast<void *>(uctx->uc_mcontext->__ss.__eip);
#elif defined(__loongarch__)
        error_addr = reinterpret_cast<void *>(uctx->uc_mcontext.__pc);
#else
#warning ":/ sorry, ain't know no nothing none not of your architecture!"
#endif
        if (error_addr) {
            st.load_from(error_addr, 32, reinterpret_cast<void *>(uctx),
                         info->si_addr);
        } else {
            st.load_here(32, reinterpret_cast<void *>(uctx), info->si_addr);
        }

        Printer printer;
        printer.address = true;
        printer.print(st, stderr);

#if (defined(_XOPEN_SOURCE) && _XOPEN_SOURCE >= 700) ||                        \
    (defined(_POSIX_C_SOURCE) && _POSIX_C_SOURCE >= 200809L)
        psiginfo(info, nullptr);
#else
        (void)info;
#endif
    }

  private:
    details::handle<char *> _stack_content;
    bool _loaded;

#ifdef __GNUC__
    __attribute__((noreturn))
#endif
    static void
    sig_handler(int signo, siginfo_t *info, void *_ctx) {
        handleSignal(signo, info, _ctx);

        // try to forward the signal.
        raise(info->si_signo);

        // terminate the process immediately.
        puts("watf? exit");
        _exit(EXIT_FAILURE);
    }
};

#endif // BACKWARD_SYSTEM_LINUX || BACKWARD_SYSTEM_DARWIN

#ifdef BACKWARD_SYSTEM_WINDOWS

class SignalHandling {
  public:
    SignalHandling(const std::vector<int> & = std::vector<int>())
        : reporter_thread_([]() {
              /* We handle crashes in a utility thread:
                backward structures and some Windows functions called here
                need stack space, which we do not have when we encounter a
                stack overflow.
                To support reporting stack traces during a stack overflow,
                we create a utility thread at startup, which waits until a
                crash happens or the program exits normally. */

              {
                  std::unique_lock<std::mutex> lk(mtx());
                  cv().wait(lk,
                            [] { return crashed() != crash_status::running; });
              }
              if (crashed() == crash_status::crashed) {
                  handle_stacktrace(skip_recs());
              }
              {
                  std::unique_lock<std::mutex> lk(mtx());
                  crashed() = crash_status::ending;
              }
              cv().notify_one();
          }) {
        SetUnhandledExceptionFilter(crash_handler);

        signal(SIGABRT, signal_handler);

        // Requires -lucrt, which can conflict with other *rt libraries, so
        // let's just comment it out. This is fine since this just silences some
        // abort message
        //
        //_set_abort_behavior(0, _WRITE_ABORT_MSG | _CALL_REPORTFAULT);

        std::set_terminate(&terminator);
#ifndef BACKWARD_ATLEAST_CXX17
        std::set_unexpected(&terminator);
#endif
        _set_purecall_handler(&terminator);
        _set_invalid_parameter_handler(&invalid_parameter_handler);
    }
    bool loaded() const { return true; }

    ~SignalHandling() {
        {
            std::unique_lock<std::mutex> lk(mtx());
            crashed() = crash_status::normal_exit;
        }

        cv().notify_one();

        reporter_thread_.join();
    }

  private:
    static CONTEXT *ctx() {
        static CONTEXT data;
        return &data;
    }

    enum class crash_status { running, crashed, normal_exit, ending };

    static crash_status &crashed() {
        static crash_status data;
        return data;
    }

    static std::mutex &mtx() {
        static std::mutex data;
        return data;
    }

    static std::condition_variable &cv() {
        static std::condition_variable data;
        return data;
    }

    static HANDLE &thread_handle() {
        static HANDLE handle;
        return handle;
    }

    std::thread reporter_thread_;

    // TODO: how not to hardcode these?
    static const constexpr int signal_skip_recs =
#ifdef __clang__
        // With clang, RtlCaptureContext also captures the stack frame of the
        // current function Below that, there are 3 internal Windows functions
        4
#else
        // With MSVC cl, RtlCaptureContext misses the stack frame of the current
        // function The first entries during StackWalk are the 3 internal
        // Windows functions
        3
#endif
        ;

    static int &skip_recs() {
        static int data;
        return data;
    }

    static inline void terminator() {
        crash_handler(signal_skip_recs);
        abort();
    }

    static inline void signal_handler(int) {
        crash_handler(signal_skip_recs);
        abort();
    }

    static inline void __cdecl invalid_parameter_handler(const wchar_t *,
                                                         const wchar_t *,
                                                         const wchar_t *,
                                                         unsigned int,
                                                         uintptr_t) {
        crash_handler(signal_skip_recs);
        abort();
    }

    NOINLINE static LONG WINAPI crash_handler(EXCEPTION_POINTERS *info) {
        // The exception info supplies a trace from exactly where the issue was,
        // no need to skip records
        crash_handler(0, info->ContextRecord);
        return EXCEPTION_CONTINUE_SEARCH;
    }

    NOINLINE static void crash_handler(int skip, CONTEXT *ct = nullptr) {

        if (ct == nullptr) {
            RtlCaptureContext(ctx());
        } else {
            memcpy(ctx(), ct, sizeof(CONTEXT));
        }
        DuplicateHandle(GetCurrentProcess(), GetCurrentThread(),
                        GetCurrentProcess(), &thread_handle(), 0, FALSE,
                        DUPLICATE_SAME_ACCESS);

        skip_recs() = skip;

        {
            std::unique_lock<std::mutex> lk(mtx());
            crashed() = crash_status::crashed;
        }

        cv().notify_one();

        {
            std::unique_lock<std::mutex> lk(mtx());
            cv().wait(lk, [] { return crashed() != crash_status::crashed; });
        }
    }

    static void handle_stacktrace(int skip_frames = 0) {
        // printer creates the TraceResolver, which can supply us a machine type
        // for stack walking. Without this, StackTrace can only guess using some
        // macros.
        // StackTrace also requires that the PDBs are already loaded, which is
        // done in the constructor of TraceResolver
        Printer printer;

        StackTrace st;
        st.set_machine_type(printer.resolver().machine_type());
        st.set_thread_handle(thread_handle());
        st.load_here(32 + skip_frames, ctx());
        st.skip_n_firsts(skip_frames);

        printer.address = true;
        printer.print(st, std::cerr);
    }
};

#endif // BACKWARD_SYSTEM_WINDOWS

#ifdef BACKWARD_SYSTEM_UNKNOWN

class SignalHandling {
  public:
    SignalHandling(const std::vector<int> & = std::vector<int>()) {}
    bool init() { return false; }
    bool loaded() { return false; }
};

#endif // BACKWARD_SYSTEM_UNKNOWN

} // namespace backward

#endif /* H_GUARD */
